Abstract: Based on the daily precipitation and runoff data of six main embranchments (Haicheng River, Nansha River, Beisha River, Lanhe River, Xihe River, and Taizi River south embranchment) of Taizi River basin in 1967-2006, this paper analyzed the variation trend of runoff coefficient of the embranchments as well as the relationship between this variation trend and precipitation. In 1967-2006, the Taizi River south embranchment located in alpine hilly area had the largest mean annual runoff coefficient, while the Haicheng River located in plain area had the relatively small one. The annual runoff coefficient of the embranchments except Nansha River showed a decreasing trend, being more apparent for Taizi River south embranchment and Lanhe River. All the embranchments except Xihe River had an obvious abrupt change in the annual runoff coefficient, and the beginning year of the abrupt change differed with embranchment. Annual precipitation had significant effects on the annual runoff coefficient.

Key words: runoff coefficient, Mann-Kendall test, abrupt change, Taizi River basin