According to this line How to speed up pdflatex for a very large document on MacOS X? . Precompile preamble significantly speed up pdflatex compilation.
The method is to generate a
precompile.fmt file( which is 6MB in my case), then copy it to the folder contains the tex file, and add
%&precompile to the first line of tex file.
I did so, and found it really speed up the compilation. But since the
precompile.fmt file is a little bit large. I think to copy it to every tex folder is really a waste of disk space. So is there a way to load the same
precompile.fmt file from the same location in different tex file?