In order to better apply the API model and Xin’anjiang model to the ungauged regions, the parameter regionalization study and its application were conducted in this paper. Here, the API model and Xin’anjiang model were applied to small and medium-sized basins in the Dabie Mountain area and South Anhui Mountain area, the regional regularity of model parameters in the selected area was studied, and the result of regionalization was verified by the new hydrological station for the small and medium-sized rivers. The results show that both API model and Xin’anjiang model can be used to simulate the flood runoff in the study area; stepwise regression analysis can effectively deduce the sensitive parameters; based on the parameter regionalization method combining spatial proximity and stepwise regression analysis, the average deterministic coefficients for hourly API model and Xin’anjiang model simulations in the new hydrological station are 0. 92 and 0. 86, respectively. Therefore, this method can effectively deduce the parameters of API model and Xin’anjiang model in the ungauged basins of selected area.