Response of glacier runoff to climate warming in the past 27 a was analyzed using precipitation, glacier mass balance and discharge measured in the Glacier No.1 at the headwater of the rümqi River, Tianshan mountains. Summer air temperature increased by 0.20 ℃·(10a)^-1 during 1959-2006, with a pronounced increase (0.9 ℃) in the period of 1996-2006, as compared with the period of 1980-1995. Pearson correlation coefficient between annual discharge and summer air temperature was higher after 1995 than that before 1995. Distinct climate warming led to 349.2 mm decrease in glacier mass balance from the period of 1980-1995 to the period of 1996-2006, even though annual precipitation increased about 84.8 mm (18.1%). As a result, annual runoff in the basin increased 37.3%, of which 12.3% was due to precipitation increase and 26.9% was due to glacier mass loss. 1.0℃ increase in summer air temperature would result in about 486 mm increase glacier mass loss, and 470 mm increase in glacier runoff or 104% increase of glacier runoff in glacier stable condition. Same results can be seen in the analyses of basin water balance, relationship between summer air temperature and glacier mass balance and annual runoff.