Debris flow disaster occurred frequently, at the same time it covered a wide area in China. Through statistics analyzing debris flow disaster data from 1914 to 1999, obtain that debris flow hazards mainly distributed in the east longitude 100-110, 25-300 north latitude and 30-35 north latitude in China. This region is mainly affected by subtropical climate and central Asia humid tropical monsoon climate, such climate have little rainfall in winter but intense rainfall in summer, due to the complex topography and different monsoon circulation, the frequency of debris flow occurrence in this area is much higher than other areas. After the earthquake in May 12, 2008, the slope material structure are destroyed which in turn provide adequate loose clastic-sediment for debris flow to initiate, several years later the loose clastic-sediment may reconsolidate again and reach new balance. Compare the frequency and scale of debris flow before and after the earthquake, know that after earthquake the frequency and scale of debris flow are much serious than the events occurred before earthquake, then gradually tend to stable. Based on these phenomena could predict the scale and trend in the future, at the same time it could provide reference for debris flow prevention and reduction, and then reduce the loss that caused by debris flow hazards.