Based on topography and forecasted 3-hour wind fields, relative humidity fields initialed from 20:00 BST and 08:00 BST by using the SWCWARMS (southwest center WRF ADAS real-time modeling system), the precipitation correction equation was constructed by calculating the terrain precipitation estimates combined with precipitation fields forecasted by SWCWARMS. The daily precipitation, precipitation processes in Sichuan Basin and in western Sichuan Basin during flood season from June to August during 2018-2020 are corrected, and the precipitation in the steep terrain transition zone from the eastern slope of western Sichuan Plateau to the western Sichuan Basin was tested and evalcated only. The results are as follows: (1) The TS of the precipitation correction value with each magnitude was improved compared with TS of forecasted precipitation by the SWCWARMS. The correction effect of precipitation forecasted initialed from 20:00 BST was better than that initialed from 08:00, and the correction effect of the precipitation processes in western Sichuan Province was the best for heavy rain and above. Compared with the SWCWARMS, the relative improvement rates of TS of corrected value of precipitation with heavy rain, torrential rain and heavy downpour were 19%, 25% and 37%, respectively, the hit ratio was higher, the false alarm rate and miss rate were decreased significantly. (2) The correction equations of precipitation had a good correction effect on both torrential rain and general precipitation cases of precipitation processes in western Sichuan Province occurring in the steep terrain transition zone, even for cases of precipitation area predicted by the SWCWARMS was far from the actual situation.