There are 2500+ Chinese characters in common use, compared to 26 characters of roman alphabets. As a result, in a category page, most indexing sets consists of only one member, losing the purpose of sorting. For an example see
https://zh.wikipedia.org/wiki/Category:數學分析
The community guideline recommends manually indexing pages by it's pinyin (spelling of characters by roman alphabets), that is, use the syntax [[微積分 | W ]], here 微 is spelled as "wei".
Mediawiki should do this automatically.