Setting and displaying content in its proper language is a key factor to get higher international ranking. Based on ISO 639-2 Standard Language Codes, the best practice is to:
Use these language codes in your lang attribute on the html tag to define the language of your HTML or XHTML document.
In case you are going to tap into China market by developing a site for China users, it’s advised to create a mirror site in China out of the speed consideration. Page speed is a major parameter for search engine for ranking especially Google has recently devoted a unique section in Google Analytic to assist webmaster, bloggers and web site operators to improve the health of its site
Don’t forget to localize your language. Even in China, there are many different slang and languages they are using in different provinces and cities. Find a local team to create content or work out the structure for your Chinese site.