diff --git a/README.md b/README.md
index baea811..b1d3168 100644
--- a/README.md
+++ b/README.md
@@ -100,6 +100,9 @@ iikira/BaiduPCS-Go was largely inspired by [GangZhuo/BaiduPCS](https://github.co
 [离线下载](#离线下载), 支持http/https/ftp/电驴/磁力链协议.
 
 # 版本更新
+**2022.2.18** v3.8.7:
+- fix #175, 在正式上传前即进行文件大小检测
+
 **2022.2.14** v3.8.6:
 - fix #160 #173, 修复上传出现空文件的bug
 - fix #165, 支持自带提取码的转存链接
diff --git a/baidupcs/prepare.go b/baidupcs/prepare.go
index 8523d87..6316ed5 100644
--- a/baidupcs/prepare.go
+++ b/baidupcs/prepare.go
@@ -288,7 +288,7 @@ func (pcs *BaiduPCS) prepareRapidUpload(targetPath, contentMD5, sliceMD5, crc32
 // PrepareRapidUpload 秒传文件, 只返回服务器响应数据和错误信息
 func (pcs *BaiduPCS) PrepareRapidUpload(targetPath, contentMD5, sliceMD5, crc32 string, length int64) (dataReadCloser io.ReadCloser, pcsError pcserror.Error) {
 	pcs.lazyInit()
-	pcsError = pcs.checkIsdir(OperationRapidUpload, targetPath, "", length)
+	pcsError = pcs.CheckIsdir(OperationRapidUpload, targetPath, "", length)
 	if pcsError != nil {
 		return nil, pcsError
 	}
@@ -299,7 +299,7 @@ func (pcs *BaiduPCS) PrepareRapidUpload(targetPath, contentMD5, sliceMD5, crc32
 // PrepareRapidUploadV2 秒传文件, 新接口
 func (pcs *BaiduPCS) PrepareRapidUploadV2(targetPath, contentMD5 string, length int64) (dataReadCloser io.ReadCloser, pcsError pcserror.Error) {
 	pcs.lazyInit()
-	pcsError = pcs.checkIsdir(OperationRapidUpload, targetPath, "", length)
+	pcsError = pcs.CheckIsdir(OperationRapidUpload, targetPath, "", length)
 	if pcsError != nil {
 		return nil, pcsError
 	}
@@ -399,12 +399,12 @@ func (pcs *BaiduPCS) PrepareLocatePanAPIDownload(fidList ...int64) (dataReadClos
 }
 
 // PrepareUpload 上传单个文件, 只返回服务器响应数据和错误信息（分片上传中的预上传部分）
-func (pcs *BaiduPCS) PrepareUpload(fileSize int64, policy string, targetPath string, uploadFunc UploadFunc) (dataReadCloser io.ReadCloser, pcsError pcserror.Error) {
+func (pcs *BaiduPCS) PrepareUpload(policy string, targetPath string, uploadFunc UploadFunc) (dataReadCloser io.ReadCloser, pcsError pcserror.Error) {
 	pcs.lazyInit()
-	pcsError = pcs.checkIsdir(OperationUpload, targetPath, policy, fileSize)
-	if pcsError != nil {
-		return nil, pcsError
-	}
+	//pcsError = pcs.checkIsdir(OperationUpload, targetPath, policy)
+	//if pcsError != nil {
+	//	return nil, pcsError
+	//}
 
 	pcsURL := pcs.generatePCSURL("file", "upload", map[string]string{
 		"path":  targetPath,
@@ -462,7 +462,7 @@ func (pcs *BaiduPCS) PrepareUploadCreateSuperFile(policy string, checkDir bool,
 
 	if checkDir {
 		// 检查是否为目录
-		pcsError = pcs.checkIsdir(OperationUploadCreateSuperFile, targetPath, "", 0)
+		pcsError = pcs.CheckIsdir(OperationUploadCreateSuperFile, targetPath, "", 0)
 		if pcsError != nil {
 			return nil, pcsError
 		}
diff --git a/baidupcs/upload.go b/baidupcs/upload.go
index 5fbc9bc..e8652b2 100644
--- a/baidupcs/upload.go
+++ b/baidupcs/upload.go
@@ -201,8 +201,8 @@ func (pcs *BaiduPCS) RapidUploadNoCheckDir(targetPath, contentMD5, sliceMD5, crc
 }
 
 // Upload 上传单个文件
-func (pcs *BaiduPCS) Upload(fileSize int64, policy, targetPath string, uploadFunc UploadFunc) (pcsError pcserror.Error, newpath string) {
-	dataReadCloser, pcsError := pcs.PrepareUpload(fileSize, policy, targetPath, uploadFunc)
+func (pcs *BaiduPCS) Upload(policy, targetPath string, uploadFunc UploadFunc) (pcsError pcserror.Error, newpath string) {
+	dataReadCloser, pcsError := pcs.PrepareUpload(policy, targetPath, uploadFunc)
 	if pcsError != nil {
 		return pcsError, ""
 	}
diff --git a/baidupcs/util.go b/baidupcs/util.go
index 0ef5fc4..e830358 100644
--- a/baidupcs/util.go
+++ b/baidupcs/util.go
@@ -27,7 +27,7 @@ func (pcs *BaiduPCS) Isdir(pcspath string) (fileSize int64, isdir bool, pcsError
 	return f.Size, f.Isdir, nil
 }
 
-func (pcs *BaiduPCS) checkIsdir(op string, targetPath string, policy string, fileSize int64) pcserror.Error {
+func (pcs *BaiduPCS) CheckIsdir(op string, targetPath string, policy string, fileSize int64) pcserror.Error {
 	// 检测文件是否存在于网盘路径
 	// 很重要, 如果文件存在会直接覆盖!!! 即使是根目录!
 	onlineSize, isdir, pcsError := pcs.Isdir(targetPath)
diff --git a/internal/pcsfunctions/pcsupload/upload.go b/internal/pcsfunctions/pcsupload/upload.go
index 7ecb78c..97c3e50 100644
--- a/internal/pcsfunctions/pcsupload/upload.go
+++ b/internal/pcsfunctions/pcsupload/upload.go
@@ -47,9 +47,10 @@ func (pu *PCSUpload) lazyInit() {
 	}
 }
 
-// Precreate 检查网盘的目标路径是否已存在同名文件
-func (pu *PCSUpload) Precreate() (err error) {
-	return nil
+// Precreate 检查网盘的目标路径是否已存在同名文件及路径合法性
+func (pu *PCSUpload) Precreate(fileSize int64, policy string) pcserror.Error {
+	pcsError := pu.pcs.CheckIsdir(baidupcs.OperationUpload, pu.targetPath, policy, fileSize)
+	return pcsError
 }
 
 func (pu *PCSUpload) TmpFile(ctx context.Context, partseq int, partOffset int64, r rio.ReaderLen64) (checksum string, uperr error) {
@@ -98,12 +99,12 @@ func (pu *PCSUpload) TmpFile(ctx context.Context, partseq int, partOffset int64,
 	return checksum, pcsError
 }
 
-func (pu *PCSUpload) CreateSuperFile(fileSize int64, policy string, checksumList ...string) (err error) {
+func (pu *PCSUpload) CreateSuperFile(policy string, checksumList ...string) (err error) {
 	pu.lazyInit()
 	//newpath := ""
 	// 先在网盘目标位置, 上传一个空文件
 	// 防止出现file does not exist
-	pcsError, newpath := pu.pcs.Upload(fileSize, policy, pu.targetPath, func(uploadURL string, jar http.CookieJar) (resp *http.Response, err error) {
+	pcsError, newpath := pu.pcs.Upload(policy, pu.targetPath, func(uploadURL string, jar http.CookieJar) (resp *http.Response, err error) {
 		mr := multipartreader.NewMultipartReader()
 		mr.AddFormFile("file", "file", &EmptyReaderLen64{})
 		mr.CloseMultipart()
diff --git a/main.go b/main.go
index 7799c59..ec67b85 100644
--- a/main.go
+++ b/main.go
@@ -55,7 +55,7 @@ const (
 
 var (
 	// Version 版本号
-	Version = "v3.8.6-devel"
+	Version = "v3.8.7-devel"
 
 	historyFilePath = filepath.Join(pcsconfig.GetConfigDir(), "pcs_command_history.txt")
 	reloadFn        = func(c *cli.Context) error {
diff --git a/requester/uploader/multiuploader.go b/requester/uploader/multiuploader.go
index 26dbf39..3df3797 100644
--- a/requester/uploader/multiuploader.go
+++ b/requester/uploader/multiuploader.go
@@ -2,6 +2,7 @@ package uploader
 
 import (
 	"context"
+	"github.com/qjfoidnh/BaiduPCS-Go/baidupcs/pcserror"
 	"github.com/qjfoidnh/BaiduPCS-Go/pcsutil"
 	"github.com/qjfoidnh/BaiduPCS-Go/pcsutil/converter"
 	"github.com/qjfoidnh/BaiduPCS-Go/requester"
@@ -14,9 +15,9 @@ import (
 type (
 	// MultiUpload 支持多线程的上传, 可用于断点续传
 	MultiUpload interface {
-		Precreate() (err error)
+		Precreate(fileSize int64, policy string) (err pcserror.Error)
 		TmpFile(ctx context.Context, partseq int, partOffset int64, readerlen64 rio.ReaderLen64) (checksum string, terr error)
-		CreateSuperFile(fileSize int64, policy string, checksumList ...string) (cerr error)
+		CreateSuperFile(policy string, checksumList ...string) (cerr error)
 	}
 
 	// MultiUploader 多线程上传
diff --git a/requester/uploader/multiworker.go b/requester/uploader/multiworker.go
index 2286b2b..3eb8b5f 100644
--- a/requester/uploader/multiworker.go
+++ b/requester/uploader/multiworker.go
@@ -37,6 +37,10 @@ func (werl *workerList) Readed() int64 {
 }
 
 func (muer *MultiUploader) upload() (uperr error) {
+	err := muer.multiUpload.Precreate(muer.file.Len(), muer.config.Policy)
+	if err != nil {
+		return err
+	}
 	var (
 		uploadDeque = lane.NewDeque()
 	)
@@ -120,7 +124,7 @@ func (muer *MultiUploader) upload() (uperr error) {
 	default:
 	}
 
-	cerr := muer.multiUpload.CreateSuperFile(muer.file.Len(), muer.config.Policy, muer.workers.CheckSumList()...)
+	cerr := muer.multiUpload.CreateSuperFile(muer.config.Policy, muer.workers.CheckSumList()...)
 	if cerr != nil {
 		return cerr
 	}