Precipitation is the input data for hydrological analysis and computation. The hydrological simulation of precipitation distribution has a direct influence on the precision of hydrological analysis results. It is very important for storm analysis to have the central position of precipitation and the point precipitation quantity in the center. However, there is little study on this aspect. According to the research on the present precipitation models, based on the theory that the natural precipitation spatial distribution without the effect of terrain is a group of concentric ovals on the flat earth surface and has a definite center where has maximum precipitation, this paper introduces how to establish a new distributed precipitation model which can simulate the position of precipitation center and the point precipitation quantity. Moreover, the effect of terrain on precipitation is modified with Lagrange interpolation in this paper. The model can simulate the position of the precipitation center and the point precipitation quantity. Therefore, it has practical value in the field of watershed storm analysis, real-time flood forecasting, runoff producing and concentration. The practice indicates that the model has a high precision.