By using the hourtohour rainfall data from automatic weather stations and the inflow of Zhouning Reservoir in Fujian from 2008 to 2012， 30 precipitation cases are selected, and the average area rainfall over the Zhouning Reservoir drainage basin is calculated with 12 differential estimation methods based on the secondary development of Surfer 8.0. The numerical estimates and the spatial distribution characteristics of the regional rainfall are analyzed to find a relatively convenient, effective and accurate computational method. The results show that in various interpolation algorithm methods, the mean relative errors of Modified Quadratic, Kriging, and Radial Basis Function are obviously lower. Further research illustrates that the first selected interpolation algorithm for the area rainfall of <20 m is the Radial Basis Function method, while for the area rainfall of >60mm, Kriging is the best.