Abstract: The CLIGEN weather generator is a part of the Water Erosion Prediction Project (WEPP) model. It is applied to forecast weather condition and fill the missing weather data. However, the CLIGEN was specially developed for working under the weather conditions of the United States, and the accuracy cannot be ensured when used in other places. We analyzed and assessed the precision of the daily and monthly weather data based on the comparison between the data simulated by CLIGEN and the daily observation data according to five national meteorological stations (Tuotuohe, Maerkang, Lijiang, Dujiangyan and Shapingba) in the upper Yangtze River. The results indicated that the input weather parameters in CLIGEN can significantly affect the simulation results. The data generated by CLIGEN are generally in consistence with those from the five stations in the upper Yangtze River. The daily data simulated by CLIGEN have marked error while the monthly data are more accurate than daily data. The simulated monthly temperature is lower than the true values. The absolute and relative errors of parts of simulated data vary among different months.