Hainan island lies in the tropics and the subtropics, it belongs to the area of the monsoon climate. The paper uses the remote sensing technique to systematically research Hainan island land desertification and its law. By interpreting TM image and some aero color infrared photo, the paper gives us the land desertification distribution area, it has the feature that the desertification is worst in west and light in east, and the farther away from the sea, the lighter it is. In order to enhance the useful imformation, some methods of image processing were used. At the same time, the reason and development trend of Hainan island land desertification is discussed and the cure method is also put forword in this paper.