Runoff formation is a complex meteorologicalhydrologicalprocess impacted by many factors, especially in the inland river basin. Based on the data of daily mean air temperature, precipitation and runoff during the period of 19582007 in the Kaidu River watershed, this paper analyzed the changes in air temperature, precipitation and runoff and revealed the direct and indirect impacts of daily air temperature and precipitation on daily runoff by path analysis. The results showed that meantemperature time series of the annual, summer and autumn had a significant fluctuant increase during the last 50 years (P<0.05). Only winter precipitation increased significantly (P < 0.05) with a rate of 1.337 mm/10a. The annual and winter runoff depthes in the last 50 years significantly increased with the rates of 7.11 mm/10a and 1.85 mm/10a, respectively. The driving function of both daily temperature and precipitation on daily runoff in annual and seasonal levels is significant in the Kaidu River watershed by correlation analysis. The result of path analysis showed that the positive effect of daily air temperature on daily runoff depth is much higher than that of daily precipitation in annual, spring, autumn and winter, however, the trend is opposite insummer.