Abstract: The historical rainfall records of Sichuan and Yunnan provinces during 1990-2001 were used to analyze the mean annual precipitation(MAP), the daily mean precipitation of rainy season(DMPRS) and DMPRS's variability, and then analyze the relationship between above indices and the distribution of debris flow ravines further, aiming at probing into the relationship between precipitation variance and debris flow ravine distribution in Sichuan and Yunnan provinces.The results show that although DMPRS has small fluctuation, it has relative stability in different regions.Furthermore, the fluctuation magnitude of it has close relationship with the distribution of debris flow ravines, and the correlation coefficient is as high as 0.864.These results show that the DMPRS can be considered as a criterion to develope new rainfall threshold model for debris flow forecasting.