The Tailan River rises in the southern piedmont of the Tomor Peak in the southwest Tianshan Mountains, - and some modern glaciers are distributed in the headwaters of the Tailan River. The Tailan Hydrologic Station is located at the debouchure of the river, and the area upstream from the station is 1 324 km~2. In this study, the variation of mean annual runoff volume at Tailan Hydrologic Station during the period of 1957 -2011 was analyzed using the SPSS Statistical Product and Service Solutions programs. The results revealed that the annual distribution of runoff and precipitation was quite uneven, runoff occurred mainly in summer and autumn, and precipitation mainly in spring and summer. A trend regression model was developed after recognizing and extracting the trend function QS (t) of the time series of mean annual runoff volume of the Tailan River. The annual runoff volume of the Tailan River was in decrease during the period of 1957 - 1981, increase during the period of 1981 -1999, and decrease again during the period of 1999 - 2011.Precipitation and temperature were the main factors resulting in the variation of annual runoff volume of the Tailan River, and the change of annual runoff volume was similar to the variation of precipitation and temperature.