A heavy rain event in Oct.2000 of Hainan Island is simulated with numerical model MM5. The result indicates that the event occured at the stream convergence area of South China Sea depression and north cold air. The length of convergence area is about 800km from west to east. The convergence of warm and cold air produced the strong ascending motion, then derived the heavy rain in the large area. The precipitation in Hainan Island is a part of the event. Furthermore, the convergence area possesses the characteristics of the weak cold front.