Can't see the Chinese characters in VIM

you are not using a font which contains the glyphs needed to display the characters you typed.

so, choose the right font via

:set guifont=*

or

:set guifontwide=*

which would pop up a font-selection-dialog. and once you have a working font make it permanent by putting

set guifont=YOURFONT

to your .gvimrc / .vimrc