Abstract: Based on HEC-HMS hydrology model and ArcGIS platform, after pretreating the DEM data at 30 m resolution and extracting the digital basin for the Yidie River basin, we divided the basin into 17 sub-basins and generated fundamental hydrology computing elements with the combination of the corresponding land utilization and agrotype data to simulate the precipitation-runoff process in the basin. Due to the complex underlying surface, 2 simulation schemes were employed to analyze the influence of different confluence processes on flood. In scheme one, the calculations of runoff yield and runoff were calculated by initial loss and steady seepage method and kinematic wave method respectively and the flood was routed by Muskingum method; in scheme two, the runoff yield and runoff were calculated by SCS curve method and SCS unit hydrograph method respectively and the flood was routed by Muskingum method. The results show that the flood peak qualification rate of the first scheme is 88.9%, the average DC is 0.773, and the flood peak appearance time difference is 10 min; while the flood peak qualification rate of the second scheme is 89.9%, the average DC is 0.838, and the flood peak appearance time difference is 8 min. All above results point out that the hydrological model could be well applied in the Yidie River Basin and is of great significance for the application of HEC-HMS hydrological model in this area.