Abstract: Based on the CMPAS three source precipitation fusion products and precipitation data of more than 5000 meteorological stations in Sichuan Province, the quality of precipitation fusion products was evaluated for the monitoring of 13 regional rainstorm processes in Sichuan by using element error analysis, method for object-based diagnostic evaluation and other methods. The results showed that: (1) The average relative error of the fusion products in hourly precipitation monitoring of regional rainstorm process was significantly related to the number of actual precipitation peaks. For each additional precipitation peak, the average relative errors of 1 km and 5 km fusion products increased by 1.2% and 1.6%, respectively. (2) Compared with the 5 km fusion product, the correlation coefficient between the hourly precipitation of regional rainstorm monitored by the 1 km fusion product and the actual precipitation increased by 4%, the deviation decreased by 4%, and the average absolute error and root mean square error decreased by 40%. (3) The precipitation fusion products mainly overestimated the hourly precipitation in the range of 0.1~1.9 mm and underestimated the hourly precipitation in the range of ≥5 mm. (4) The 1 km and 5 km fusion products had high accuracy in monitoring the spatial position, trend, structure and scope of regional rainstorm processes. The average centroid distance between the regional rainstorm assessed by 1 km and 5 km fusion products and the actual precipitation was less than 5 km, the average axial angle difference was less than 2°, the eccentricity deviation was between 0 and 0.12, and the average area ratio was about 1.10.