Compared to general rainfall events, sudden rainfall has always been a challenge and focus of weather forecasting and research. In mid-July 2022, sudden heavy rainfall occurred in the northwest of the Sichuan Basin, resulting in the severe disasters. To better understand the causes of such rainfall events, a comparative analysis of the physical environment and dynamic characteristics of these two sudden rainfall events is conducted based on observational data and ERA5 reanalysis data. The results showed that both temperature and moisture environments of the events exhibited sudden changes. Before the onset of rainfall event, energy, moisture, and instability are increased explosively in a short period, reaching extreme conditions. Intense upward motion occurred as mid-to-upper-level cyclonic vorticity developed downward to the lower levels. Rainfall events is occurred during the optimal period when vorticity and moisture were coupled, with a good correspondence between the maximum wet vorticity area and the rainfall area, indicating the diagnostic significance of wet vorticity for identifying rainfall areas.