diff --git a/beamerinnerthemesjtubeamer.sty b/beamerinnerthemesjtubeamer.sty
index e3e79431..0a9f95ea 100644
--- a/beamerinnerthemesjtubeamer.sty
+++ b/beamerinnerthemesjtubeamer.sty
@@ -90,9 +90,7 @@
     \titlegraphic{\sjtubg[opacity=0.2]}
     \setbeamertemplate{background}
     {
-      \bgcenterbox{
-        \resizebox{0.95\paperwidth}{!}{\sjtubg[opacity=0.2]}
-      }
+      \parbox[c][1.1\paperheight][c]{\paperwidth}{\centering\resizebox{\paperwidth}{!}{\sjtubg[cprimary!50,opacity=0.2]}}
     }
   \else
     \if\EqualOption{inner}{cover}{min}
diff --git a/src/doc/cover.tex b/src/doc/cover.tex
index 572b15ad..326411da 100644
--- a/src/doc/cover.tex
+++ b/src/doc/cover.tex
@@ -2,8 +2,8 @@
 \usepackage{pdfpages}
 \includepdfset{fitpaper=true,pages=1-last}
 \begin{document}
-\includepdf[nup=3x3,frame=true]{cover-red-dark.pdf}
-\includepdf[nup=3x3,frame=true]{cover-red-light.pdf}
-\includepdf[nup=3x3,frame=true]{cover-blue-dark.pdf}
-\includepdf[nup=3x3,frame=true]{cover-blue-light.pdf}
+\includepdf{cover-red-dark.pdf}
+\includepdf{cover-red-light.pdf}
+\includepdf{cover-blue-dark.pdf}
+\includepdf{cover-blue-light.pdf}
 \end{document}
diff --git a/src/doc/sjtubeamer.tex b/src/doc/sjtubeamer.tex
index ab6cfb49..de5b3930 100644
--- a/src/doc/sjtubeamer.tex
+++ b/src/doc/sjtubeamer.tex
@@ -544,6 +544,6 @@ \chapter*{许可证}
 
 \vfill
 
-{\small \themename{} \hfill \today}
+{\small \themename{} \hfill  SJTUG  \hfill \today}
 
 \end{document}
\ No newline at end of file
diff --git a/src/source/beamerinnerthemesjtubeamer.dtx b/src/source/beamerinnerthemesjtubeamer.dtx
index d49dec54..981dd771 100644
--- a/src/source/beamerinnerthemesjtubeamer.dtx
+++ b/src/source/beamerinnerthemesjtubeamer.dtx
@@ -159,7 +159,7 @@
 %  \end{macro}
 %
 %  \begin{macro}{\bgcenterbox}
-%   Define a command to make a centered background box easily.
+%   Define a command for USERS to make a centered background box easily.
 %    \begin{macrocode}
 \newcommand{\bgcenterbox}[1]{
   \let\oldlogocolor=\sjtubeamer@logocolor%
@@ -196,9 +196,7 @@
     \titlegraphic{\sjtubg[opacity=0.2]}
     \setbeamertemplate{background}
     {
-      \bgcenterbox{
-        \resizebox{0.95\paperwidth}{!}{\sjtubg[opacity=0.2]}
-      }
+      \parbox[c][1.1\paperheight][c]{\paperwidth}{\centering\resizebox{\paperwidth}{!}{\sjtubg[cprimary!50,opacity=0.2]}}
     }
   \else
 %</max>