Abstract: The data accuracy of the DEM and land cover affects the simulation performance of hydrological models. In this study, three hydrological stations, i.e. Maojiahe, Yangjiaping and Zhangjiashan, were selected as the control sites to investigate the influence of the accuracy of the input data on the simulation effect of runoff and sediment.100 SWAT models were constructed using nine different resolutions of DEM（30-3 000 m） and land cover data（30-3 000 m） and the TOPSIS method was used to evaluate the model’s performance in a comprehensive manner. The results shows that the DEM resolution affects the extraction of watershed boundary and river network, and the watershed feature information will be lost with the decrease of resolution; when the DEM resolution is lower than 1 000 m, the “Burn in” tool in SWAT needs to be used to complete the accurate extraction of watershed boundary and river network; the number of HRU decreases with the decrease of DEM resolution, whereas the influence of land cover resolution on the number of HRU is not significant; DEM causes a greater impact on parameter sensitivity than land cover when there is a large change in resolution; the optimal resolution combinations of DEM and land cover for the three models of Maojiahe, Yangjiaping and Zhangjiashan are 750 m and 300 m, 30 m and 90 m, 150 m and 3 000 m respectively. This study can provide theoretical and technical support for the construction of watershed models and the improvement of simulation accuracy.