Abstract: The shrinkage of mountain glaciers in the 20th century has been occurring on a global scale，and the rate of shrinkage of most glaciers appears to have been accelerated during the past two or three decades. Observations of Urumqi Glacier No. 1 were initiated in 1959，implemented by the Tianshan Glaciological Station，Chinese Academy of Sciences. As the longest series data in China and a reference glacier in the World Glacier Monitoring Service glacier monitoring network，Urumqi Glacier No.1 provides the longest glaciological and climatological monitoring record in China. This paper is intended to analyze the mass balance of Glacier No.1 to identify its response to the changes in temperature and precipitation. The techniques of glacier mass balance measurements using a standardized method have been described by Meier. The mass balance is calculated by contour maps of accumulation，ablation，and additional snow pits. Comparisons of methods for mass balance calculations show that the stake network generally provides accurate estimates of glacier mass balance. The total mass balance of the glacier （bn） can be obtained by the area-weighted method for all altitude zones. Based on the past 51 years of mass balance observation data, some results were obtained. The mass balance process of Tianshan Mountains Glacier No.1 experienced glacier nine times positive balance fluctuation and nine times negative balance fluctuation，the rates of negative balance years with positive balance years are 35∶16. With global warming，the Urumqi Glacier No.1 is retreating and thinning rapidly，especially from 1997 to 2009，there are continuous 12 negative balance observation years at Tianshan Mountains Glacier No.1. It shows that the Glacier No.1 in a strong negative numerical balance，and the strongest negative balance，-931 mm. w.e.，emerges from 2008 during the observation period．And what’s more，the cumulative mass balance reaches 13 709 mm. w.e. in 2008．But in 2009，the mass balance is positive，63 mm. w.e.，and the inter-annual change up to 1 062 mm. w.e.. Glacier mass balance is highly sensitive to changes in temperature and precipitation，which makes them become important indicators of climate change. When temperature reach the higher or lower，the mass balance of warm season supplied Glacier controlled by the temperature though the precipitation is great or small，Summer air temperature is the main control factors for the change of glacier mass balance. By analyzing the observation data of mass balances，air temperature and precipitation at Urumuqi Glacier No.1 between 2007/08 and 2008/09，the lower summer temperature is the main factor to result in the phenomenon. The lower summer temperature caused the start time of glacial ablation period was delayed and the end time of glacier ablation was advanced，so the loss mass reduced. And，secondly，increase annual precipitation is one of factor represent addition of mass to the glacier.

Key words: Urumuqi Glacier No.1, Positive mass balance, Summer temperature