Abstract: Satellite precipitation products provide precipitation information with broad spatial coverage, relatively high spatiotemporal resolution and convenient accessibility. Therefore, they play a significant role in addressing the limitations and uneven spatial distribution of observational data from sparse ground-based rain gauge networks. To investigate the applicability of satellite precipitation products in topographically complex regions, this study selected the catchment controlled by the Zipingpu Reservoir in the upper reaches of the Minjiang River as the study area. Based on observed precipitation and discharge data collected from 2016 to 2024, the performance of three satellite precipitation products, namely GSMaP_Gauge, IMERG-Final, and CMORPH, was systematically evaluated. The Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) model is a semi-distributed rainfall–runoff model suitable for rainfall–runoff simulation and flood forecasting. The applicability of these satellite precipitation products for precipitation monitoring and flood simulation was further assessed using HEC-HMS. To obtain a comprehensive understanding of product performance, the evaluation incorporated both continuous statistical indicators, which describe the agreement and errors in precipitation amounts, and categorical indicators, which measure the ability to identify the occurrence of precipitation events. The results show that there are significant differences in the accuracy of the three satellite precipitation products across different temporal scales. At the daily scale, IMERG-Final exhibits the best overall performance. It has the highest correlation with ground-observed precipitation, with a mean I_CC of 0.59. It also shows a relatively low I_MAE of 2.49 mm. In addition, IMERG-Final demonstrates the strongest ability to detect precipitation events, with the probability of detection generally remaining above 0.85. In comparison, the daily-scale performance of CMORPH and GSMaP_Gauge is relatively weaker. At the hourly scale, the correlation coefficients of all three satellite precipitation products decrease, indicating that the spatial heterogeneity, local variability, and short-duration characteristics of precipitation in complex mountainous terrain pose substantial challenges to satellite precipitation retrieval. Among the three products, GSMaP_Gauge shows the highest I_CC and relatively low errors at the hourly scale. Its ability to detect precipitation events is also better than that of IMERG-Final and CMORPH. Therefore, GSMaP_Gauge demonstrates a comparatively stronger capability for representing hourly precipitation processes in the study basin. The HEC-HMS model shows good applicability in the Zipingpu Reservoir-controlled catchment. The mean coefficients of determination during the calibration and validation periods are 0.75 and 0.79, respectively, indicating that the model can reasonably reproduce the observed flood processes when driven by ground-observed precipitation. Considering the results of precipitation evaluation at both daily and hourly scales, GSMaP_Gauge and IMERG-Final were selected as precipitation inputs for subsequent flood simulations. The model parameters calibrated using observed precipitation were retained, so that the impacts of satellite precipitation inputs on simulated flood processes could be directly compared. In flood simulations using the HEC-HMS model driven by satellite precipitation data, the GSMaP_Gauge precipitation product yields better simulation results than those obtained using IMERG-Final as the driving data. The qualification rate for peak discharge errors reaches 87.5%, while the qualification rate for flood volume errors reaches 100%. Furthermore, the average coefficient of determination is 0.70. The flood simulations using GSMaP_Gauge are clearly better than those using IMERG-Final, although GSMaP_Gauge still performs slightly worse than simulations driven by observed precipitation. Overall, the study results indicate that the applicability of satellite precipitation products in watersheds with complex topography varies significantly depending on product type, temporal scale, and local meteorological and topographic factors. To select an appropriate product, a comprehensive precipitation assessment combined with hydrological model-based validation is required. This study provides a technical reference for the use of satellite precipitation products in flood simulation, hydrological forecasting, and water resources management in areas where ground-based precipitation observations are lacking.