Based on XAJ model, the GIS technology and similarity analysis were used for hydrological simulations in the ungauged basins. Through correlation and cluster analysis methods, this paper determined the similar basin by the basin characteristics extraction, analyzed the relationship between the model parameters and watershed characteristics, and expounded the feasibility of parameter transformation method for the similar watersheds. The analysis of hydrological similarities indicate that the distances on the parameters of two similar watersheds are mostly small and close in the geometric space. Based on this conclusion, the hydrologic model parameters of ungauged basins were determined, and the good simulation results were achieved.