Abstract: Runoff generated at the headwaters of Urumqi River provides the principal water resource to the middle and lower reaches and Urumqi city．Study on the longterm observation of runoff change is of great significance for the reasonable utilization of water resources and development of good watershed management strategies in the arid region of northwest China．Here we systematically analyzed variation in runoff from three hydrological stations located at the source area of Urumqi River in recent 50 years，and revealed the possible causes，relating it to changes in climatic conditions and glacier mass loss．The results showed that there were generally increasing trends in runoff of these three hydrological stations; whereas the runoff of Zongkong station exhibited no significant increase over the study period．Factors influencing runoff change of three hydrological stations were different．For Glacier No.1 station，the runoff change was mainly controlled by heat conditions in glacieriezd region and the runoff showed an accelerated growth when the temperature in the melt season was more than 2 ℃．The runoff at the station included not only the immediate and direct response of glacier to climate change，but also the indirect and lagged response．And changes in volume loss of Glacier No.1 corresponded well with the runoff variations．For Empty Cirque hydrological station，the snow melt water and rainfall were source of runoff，so precipitation was the dominating factor affecting runoff change．However，the air temperature also should not be ignored．Under the condition of lower temperature and plentiful precipitation，the limited snow melt would only produce less runoff．The relation between runoff and climate change was somewhat more complicated for Zongkong station．Against the background of temperature rising and precipitation increasing，runoff showed a drop tendency in recent years which might be related to many factors，such as actual evapotranspiration enhancing，runoff peak appearing due to rapidly glacier recession，underground leakage increasing caused by extensively permafrost melts，etc.

Key words: runoff change, mechanism analysis, climate change, glacier recession, headwaters of Urumqi River