Hi, I'm afraid your question is a bit generic. First of all, what search
are you using? Did you install some extensions and/or configure
something? If not, what database are you using?
MediaWiki definitely supports Chinese search in English wikis, e.g.
<https://meta.wikimedia.org/wiki/Special:Search/%E5%88%A4%E4%BE%8B%E9%AB%94%E5%88%B6>.
Nowadays all search efforts are being spent on this extension, which
you're encouraged to try:
<https://www.mediawiki.org/wiki/Extension:CirrusSearch>
Finally, unless you're using Translate, your wiki is certainly doing
multilingualism wrong and no fancy things are really possible, because
MediaWiki is quite silly about it. Hopefully 1.25 will be better and
there are some features you can already test:
*
https://bugzilla.wikimedia.org/show_bug.cgi?id=9360
*
https://bugzilla.wikimedia.org/show_bug.cgi?id=54832
Nemo