diff --git a/CMakeLists.txt b/CMakeLists.txt
index 85ea64b71ba..ef5977889e0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -100,9 +100,9 @@ set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 set_property(GLOBAL PROPERTY PREDEFINED_TARGETS_FOLDER "cmake")
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Emscripten")
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=1024MB -s EXIT_RUNTIME=1")
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=1024MB -s EXIT_RUNTIME=1")
-    set(CMAKE_EXECUTBLE_LINKER_FLAGS "${CMAKE_EXECUTBLE_LINKER_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=1024MB -s EXIT_RUNTIME=1")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=256MB -s EXIT_RUNTIME=1")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=256MB -s EXIT_RUNTIME=1")
+    set(CMAKE_EXECUTBLE_LINKER_FLAGS "${CMAKE_EXECUTBLE_LINKER_FLAGS} -s FORCE_FILESYSTEM=1 -s INITIAL_MEMORY=256MB -s EXIT_RUNTIME=1")
 
     if(NCNN_OPENMP AND NCNN_SIMPLEOMP)
         # TODO better flags for emscripten