By working on the relations between the typhoons seen in the region of 15°-35°N and 103°-130°E from May to September, 2000-2010 and the daily precipitation amount in Sichuan in the corresponding period, this paper points out the typhoon tracks most closely related to the recorded torrential rains in Sichuan were the west track, shift track and northwest track. Comparing the ambient field of clearly seen heavy rains and not clearly seen heavy rains under the background of similar typhoon tracks, it is found that the westerlies trough was active to the north of 40°N, a high ridge was in the Central Asian region, the high pressure over the mid latitude continent controlled the area from eastern Tibetan Plateau to much of Sichuan or in the central and eastern part of China was a broad trough, which shows an unfavorable ambient field for the occurrence of obvious torrential rains in Sichuan. However, over the area between Balkhash Lake and Baikal Lake there was a broad low trough, subtropical fronts were dense and reached the area around 36°N, the mid latitude ribbon ridge line was found over the area to the south of 30°N, and moreover, the mid high latitudes in China presented a posture of east high and west low and the meridional baroclinic trough in West China was the ambient field, favorable for the breakout of rainstorms in Sichuan. The analysis results suggest that the impact of typhoons on the weather in Sichuan mainly include three aspects: the first is the indirect influence through affecting subtropical high, the second is the direct influence of the circulation in the outer area of low pressure of typhoon, and the third is that typhoon plays the role of a carrier to convey the warm and moist air to Sichuan region, interacting with the low value systems in mid high latitudes and subtropical high.