Based on in site continuous observations of mass balance over the Glacier No.1 in the source region of the Urumqi river, we analyzed the spatialtemporal variations of the surface mass balance series beginning from 1980 at each measurement sites on the glacier. Besides, attention has also been paid to variations in the glacier frontal position and the equilibrium line altitude and the relationship between mass balance and climatic factors. The source region of the Urumuqi river has seen a rising in air temperature and an increase in precipitation after the mid-1990s. Under such a pattern of climate change during the last decades, Glacier No.1 has been in an intensive mass wastage, amounted to 9599mm during 1959 and 2002, which corresponding to the thickness thinning over 10m on the glacier. An accelerating trend of mass losing on Glacier No.1 was observed to be -739.6 mm annually during 1987-2002. Variation in mass balance of the Glacier No.1 is primarily under control by the summer air temperatures, a good negative relation exists between the mass balance and the summer mean air temperature with the correlation coefficient of -0.72 at the 99% significance level. It was found that cold seasonal precipitations played a key role in the variation in winter balance. Affected by the accelerated mass wasting, the Glacier No.1 has experienced an obvious retreat at the terminus part since the 1980s, and this was more evident at the end of west branch of Glacier No.1 during 2000 and 2002. A statistical analysis showed that the accelerating retreat of the east branch might have close relation with the variations of specific mass balance in the area above 4200 m a.s.l. on Glacier No. 1.