I have created a pdf file using LaTeX. When I read it with inkscape, the styles of mathematical symbols were adjusted (maybe the font?). How do I import this pdf as is (although I know I can use the plug-in LaTeXText and re-write them). 

The style inside the original pdf:

Import to inkscape:

Pdf import settings:

See the original pdf in the attachment.

I don't know much about TeX but my quick search leads me to think that the embedded fonts might not be available throughout your system (computer). I'd try finding the fonts to install system-wide, or authoring the document with a system-wide available font.

You can try replacing all text objects within Inkscape, but I don't know what that will do to your formulae.

Thank you very much. As far as I can track, the TeX maths model uses the font Latin Modern(download).  At present, I choose the option Poppler/Cairo import(replacing all text objects within Inkscape), it is well.