You can apply for 3 months tourist visa in South Korea. You can go to Seoul to apply for it through one of travel agencies authorized by Chinese Embassy in Seoul. It takes at least 4 working days. the fee 35,000 Korean wons for single entry tourist visa valid for 3 months, however, you have to pay extra less than 20,000 wons for the service of authorized travel agency. You need prepare your original passport, fill in one visa application form of PRC, one recent passport photo

Thanks Mr Lee，

one question more
should I go myself in Seoul? can I send my passport and all papers from China directly to an agency in seoul which applies the visa for me and sent it me back in china??

Thanks

Mr. lib, I think that you can go to the Exit & Enter Department under the Beijing Public Security Bureau to apply for extension of Chinese visa, then you will get a new Chinese visa with another 30 days stay in China. If you get a visa through a travel agency in seoul but you don't go to seoul and return to China from seoul, there won't be the entry stamp on your passport for this new visa, I don't know whether it is a problem or not.