Abstract: Digital Elevation Model（ DEM）,as an important tool for characterizing the terrain features,plays a major role in the simulation of flash floods. Taking the rainfall-triggered flash flood event occurred in Guiquan Catchment located in the western mountainous area of Jingxing County,Shijiazhuang,Hebei Province on July 19,2016 as the research object,we adopted the HEC-HMS model and FLO-2D model to investigate the influence of DEM resolution on flash flood inundation simulation from aspects of flooded area and flood depth by setting five resolution schemes,which are 30 m,20 m,15 m,10 m and 5 m. Then the operational efficiency of the models were evaluated according to their respective runtime.The results show that a higher resolution of DEM leads to the decrease of flooded area and the increase of average flood depth,which in turn enhances the accuracy of the model simulation. That is,the higher the DEM resolution,the closer to the observed data the simulated flooded area and flood depth get. The accuracy of flooded area and flood depth by 30 m DEM and 5 m DEM was 0. 56 and 0. 41,0. 76 and 0. 79,respectively. As the DEM grid size decreased,the simulation accuracy increased so slowly that the difference of the simulation results（ i. e.,the flooded area and flood depth） between 5 m DEM and 10 m DEM was excessively small. The accuracy of flooded area and flood depth increased only by 2. 70% and3. 94%,respectively. However,with the decrease of the DEM gird size,the runtime of FLO-2 D increased sharply. The runtime under the 5 m DEM was 700 times longer than that under the 30 m DEM,which made the efficiency of the model much lower. Our analyses suggest that for many flash floods,a 10 m DEM presents a rational compromise between accuracy and runtime for simulating the flash flood inundation and it is more suitable for the risk assessment,early warning and forecasting of flash floods.