In order to comprehensively analyze and evaluate the monitoring capabilities of the integrated multi-satellite retrievals for global precipitation measurement (GPM) final run (IMERG-F) satellite retrieval product for daily and sub-daily scale precipitation, as well as various intensity rainfalls, under complex mountainous conditions in southwest China, ground-based dense rain gauge data was used to investigate these aspects. The results show that within the daily and sub-daily scales, the critical success index (CSI) of IMERG for short-term accumulated precipitation primarily ranges from 0.2 to 0.6, with the correlation coefficient fluctuating between 0.25 and 0.5. The daily scale precipitation detection accuracy is the highest, with better performance in summer months compared to winter. For different intensity rainfall events, IMERG exhibits a high probability of detection (POD) for light rainfall, while the false alarm rate (FAR) is relatively low. However, there is an underestimation phenomenon for moderate to heavy rainfall. The elevation difference significantly impacts the stability of IMERG products, but there is no direct linear relationship with the elevation itself. Compared to areas with significant topographic variations, IMERG-F demonstrates higher reliability in detecting weak rainfall events in areas with less topographic variation. It is concluded that the application of IMERG products in southwest China should consider the limitations imposed by seasonal and topographic characteristics.