Based on the data of tropical storm over northern Indian Ocean from the Guam Joint Typhoon Warning Center, NCEP/NCAR reanalysis data, daily precipitation data at 125 stations in Yunnan, two cases of strong Bengal Bay storm in autumn were selected, then their moving tracks and influence on precipitation over Yunnan were comparatively analyzed. It was showed these two cases with nearly the same intensities, moving track and landing position were difference. During their influence period, the intensity and range of precipitation over Yunnan were obviously different. The difference of south Asian high position on 200 hPa and steering flow resulted in various of moving track and landing position of Bengal Bay storm; the interaction of Bengal Bay storm with cold air was a critical mechanism to heavy rainfall generating in Yunnan; the moving of southwester areas at lower layer on the east side of Bengal Bay storm also played an important role in the formation of precipitation, on the one hand, it transported a large number of water vapor and energy into Yunnan, on the other hand, wind velocity convergence on gale areas was helpful to maintain necessarily dynamics condition. With the influence of the western ridge point of the western Pacific subtropical high on 500 hPa and intensity of southwesterly at lower layer, water vapor transport, intensity of convergence and maintenance time were various, different pattern in circulation at upper and lower layer caused the significant differences in dynamic structure, vertical motion and so on, while these were important reasons of various precipitation distribution generating in Yunnan with two storms.