Is it possible to extend it in China? and what are the requirements I should have to extend the L visa in China?

It is possible to extend L visa in China, the requirements are your original passport, one passport photo, the accommodation sheet issued by a local police station or by a hotel, the copy of L visa and entry record on your passport, sometimes, the financial certificate will be asked to prove that you can burden your expenses in China. Generally speaking, the L visa can be extended 30 days, it can be extended twice only. Please go to Kunming Exit-Entry Administrative Bureau.