You can go to the Exit & Enter Deparment in the city which you stay in Jiangsu Province to apply for extension of your visa, in fact, you will be issued with a visa with 0 entry and 30 or less days stay duration, it is very hard for you to get a 3 months stay duration.

what is the type of your visa now,if it is a tourist visa,extend for 3 months is possible if you only extended it once,if it is a Z visa,only can change it to a tourist visa for one month.to know more?

I think you should extend your Z visa,this is very convenient.
If you have your original two years working experience certificate,and original bachelor or higher diploma certificate,you can extend your Z-visa ,even without a employer.The total fee is 8500RMB.
If you want get 3 months visa,you should get F-visa,but you should get invitation letter,and go to Hongkong to apply one month F visa,we can extend the F visa for 3 month,the extend F visa service fee is 3700RMB.
So the price you get F visa is almost to extend your Z visa,you hold Z visa you can live in China,stay very long as you want,not just like F-visa,you need to leave mainland one year.
Hope can help you.
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