Abstract: Based on CMA-SH9 hourly rainfall data and the AWS-CMORPH merged hourly gridded precipitation products, the effects of diurnal precipitation variation forecasts in Sichuan-Chongqing region during May to September in 2020 are evaluated. The results show that the model could reproduce hourly rainfall distribution in the study area, which was less in Sichuan Basin while more around the Basin. Positive forecast deviations of hourly rainfall amount were significant from the eastern slope of Tibet Plateau to the southwest of Sichuan Basin, and in the eastern region of Sichuan Basin, which were contributed by the overestimation of rainfall frequency and intensity. The negative forecast deviations were located in Sichuan Basin, which were mainly due to the underestimation of rainfall intensity. From the eastern slope of Tibet Plateau to the east of Sichuan Basin, the peak time of observed rainfall lagged from midnight to morning, while the peak phase of forecast led that of observation. The model could reasonably capture the single peak phase pattern of precipitation in the eastern slope of Tibet Plateau and Sichuan Basin, as well as double diurnal peaks in the eastern region of Sichuan Basin, but there were still some biases between the observations and forecasts.