6-hourly precipitation data from station rain gauge records are employed to study the distribution and diurnal cycle of rainfall in the Sichuan Basin and its neighboring region of it. The results show that: There are two high rainfall centers over the peripheral mountain land of the Sichuan Basin; Nocturnal rainfall dominates this region; The peak value of daily rainfall amount in the West Sichuan Plateau mainly comes from early-midnight 6 h precipitation amount;  It  comes from night 6 h precipitation amount and frequency over the centre region of the Sichuan Basin and the western periphery of basin while the forenoon frequency and late-midnight 6 h amount dominate the northeastern periphery of the  basin. And then, mid-night heavy rainfall event during September 23~24 2008 over the basin was simulated by using the Weather Research and Forecasting Model (WRF). The mechanisms responsible for the diurnal variation of the rainfall are addressed by analyzing the model outputs. The results show that the WRF model can simulate well the spatial distribution and diurnal variation of averaged precipitation in the Sichuan Basin, the topography forcing and largescale circulation are related to the formation of mid-night maximum rainfall.