Abstract: Hydrological simulations are affected by the parameters derived from DEM, which describes the water- shed features. Xitiaoxi River basin was selected to simulate two runoff processes in Jun and Aug to Sep 2011 using the HEC-HMS model with ASTER 30 m DEM、 SRTM 90 m DEM and DEM resample data as input for HEC-geoHMS to derive the basin characteristics. The results showed that, the simulated and observed flood were fitting well and the efficiency coefficients of the model were all larger than 0.82, Uni-modal flood showed a better performance in runoff simulation than multi-modal flood. The efficiency coefficients of model based on SRTM 90 m was larger than based on ASTER 30 m DEM and resampled 90 m DEM. The efficiency coefficients of model based on resampled DEM had nonlinear relationship with DEM resolution. The relative error of HEC-HMS simulations based on ASTER 30 m DEM and SRTM 90 m DEM had a difference of 3％—5％. The relative error of simulations based on the SRTM 90 m DEM and the resampled 90 m DEM had a difference of 2％—4％.The maximum difference between the relative error of HEC-HMS simulations based on the resampled 90 m DEM was 11％.