It depends on what kind of service model your mobile phone is. If you have a dual-band or tri-band unlocked GSM phone, you can use it around China in most big cities. In China, GSM networks is operated by China Mobile providing coverage in every major city, while CDMA networks is run by China Unicom for improving its coverage.
To avoid your mobile phone not working in China, It is neccessory for you to rent a unlocked GSM cell phone such as Motolora, Nokia... in China. Then you just need a China prepaid sim card as data solution.