Based on Digital Elevation Model(DEM) in 27 small watersheds of Dabie-South Auhui mountain area, the topographic information was extracted and the average peak time lag was calculated. By establishing the mathematical model of multiple linear regression and path analysis, the influence of the factors on the flood response of the river basin is discussed. The results show the following: At the level of the valley system, shape factor and roundness, valley relative elevation, channel branching frequency and the forest coverage rate affect the basin average peak time lag mainly. And basin relative elevation is the most fundamental explanatory variables; Different geomorphic factors interaction is complex. The multiple linear regression model of average peak time lag has 73.4% explanatory. Further more,the path analysis model respectively describes influence of each variable to the average peak time lag from direct effect and indirect effect. The results can provide important reference to analysis the flood response process of South Anhui mountain area. It is significant for flood control and disaster mitigation.