Following the article below

http://blog.martinfenner.org/2014/08/25/using-microsoft-word-with-git/

安装pandoc

brew install pandoc

修改.gitattributes 文件

# .gitattributes file in root folder of your git project
*.docx diff=pandoc

修改 ~/.gitconfig 文件

# .gitconfig file in your home folder
[diff "pandoc"]
	textconv=pandoc --to=markdown
	prompt = false
[alias]
	wdiff = diff --word-diff=color --unified=1

You can then use git wdiff important_file.docx to see the changes (with deletions in red and insertions in green), or git log -p --word-diff=color important_file.docx to see all changes over time.