Normally, you're required to have a valid Chinese Visa before you travel to China.
There are special visa-free entry policies for visitors coming to China from specific countries for specific purposes and periods of time.
Hainan has extremely convenient Visa Free and Visa on Arrival policies that make it easy and quick for visitors from around the world to enter Hainan! Please visit the following link for details.
Highly suggest you to consult the Chinese Embassy/Consulate or a qualified visa application center in your city/area for professional advice on visa application. You may also visit the following link for the most appropriate visa category for your application.