Abstract: 【Objective】Investigate the influence of station density on the accuracy of PRISM interpolation, in order to elucidatethe model's scope of application.【Method】Based on the DEM of the northwest mountains of Beijing and rainfall data from the mountain automatic weather stations to calculate the result of interpolation. These results were then compared with the IDW, Kriging and Spline interpolation models using cross validation and test data validation.【Result】The precision of interpolation was reduced when site density was reduced from 0.55×10^-2 to 0.18×10^-2 sites/km² but was reduced most when using the PRISM model and least when using the Spline model. Furthermore, when the site density was reduced to 0.18×10^-2 sites/km², the error of the PRISM model was less than that of the Spline model, but still greater than the Kriging and IDW models. 【Conclusion】The present study suggests that the IDW and Kriging models should be used when stations are sparse.