以长江源区控制站直门达1978-2009 年实测径流量序列为基础，运用 Mann-Kendall 趋势分析法和滑动 T 检验方法，对径流量的趋势变化和突变进行了详细分析，并对其影响因素降水、气温和下垫面条件等进行了分析。结果表明 : 长江源区近 32 年来年径流量总体呈现增加态势，但趋势不显著，年径流序列 2004 年前后发生突变；长江源区降水序列在 2002 年前后发生突变，气温序列呈显著增加趋势，长江源区降水增加和冰雪消融是长江源区径流增加的主要原因。

The runoff data measured from 1978 to 2009 at Zhimenda hydrological station in the headwaters of Yangtze River are analyzed by Mann-Kendall test and slide T test to study the trend of runoff variation. Impacting factors including precipitation, temperature, and underlying surface condition are also elaborated in this paper. The results show that the overall annual runoff increased slightly during 1978-2009 ； while there was an abrupt change around 2004 according to slide T test. With regard to the impacting factors, the annual precipitation witnessed slight changes in general and a sudden change around 2002, and the annual air temperature series within the basin increased remarkably. It is concluded that the runoff increase during 1978-2009 is mainly caused by the increase of precipitation and ice melting.