window版本的gVim在默认情况下tab宽度为8个字符，习惯使用4个空格宽度作为tab来说有点别扭，可以找到gVim的安装目录下的_vimrc文件添加如下代码即可：

" size of a hard tabstop
set tabstop=4

" size of an "indent"
set shiftwidth=4

" a combination of spaces and tabs are used to simulate tab stops at a width
" other than the (hard)tabstop
set softtabstop=4
You may also want to try the following:

" make "tab" insert indents instead of tabs at the beginning of a line
set smarttab

" always uses spaces instead of tab characters
set expandtab

以上代码来自stackoverflow，效果不错。