Based on the annual precipitation data of north region of Shaanxi, using the moment method, maximum likelihood estimation and probability-weighted moment method, the best theoretical frequency distribution, best method of estimating parameters and annual precipitation of different frequency have been obtained by OLS standard from 12 types of frequency distribution model. The results show that LN2 and GEV have good fitting. The results can provide the basis for water conservancy project planning, design, construction and operation management.