Abstract: Urumqi Glacier No.1 is located at the headwaters of the Urumqi River in eastern Tianshan, it is one of the ten reference glaciers around the world in World Glacier Monitoring Service (WGMS). It is considered as a key element of the system because of its special geographical position in arid Central Asia. As a reference glacier in the WGMS glacier monitoring network, it provides the longest glaciological and climatological monitoring record in China. Equilibrium line altitude (ELA) is defined as the altitude where the annual mass balance is zero. Glacier behaviors such as advancing or retreating are controlled by ELA variations, and fluctuations of ELA provide an important indicator of glacier response to climate change. In practice, the ELA is a narrow zonal area, and not very easy to be identified on the glacier surface, therefore, the determination of ELA is mainly done based on the contour map of the annual mass balance of the whole glacier. This paper, based on ELA data of Urumqi Glacier No.1 during 1959-2010, studies the changing process and characteristics of ELA. The results show that ELA experienced three phases during the whole observation period. ELA presented a slow ascending trend in a normal fluctuation range before 1986, with a mean of 4051 m a.s.l; it descended slowly from 1986 to 1996, with a mean of 4035 m, however, it ascended promptly since 1997, with a mean of 4125 m. In 2010, the highest ELA was observed which surpassed the glacier summit, implying that the whole glacier was ablating in this year. During the study period, ELA range was between 3948 m and 4484 m, with a mean of 4067 m, and the general tendency was ascending continually, ascended about 90 m. Accumulation area ratio (AAR) as an important indicators of the ELA change showed obvious decreasing trend, descended by 17%. Analysis shows mass balance and ELA has significant negative correlation. When mass balance decreased by 100 mm, ELA would ascend 17 m and glacier ELA was in a steady state, namely zero ELA (ELA₀) would be 4018 m. As the net ablation increases, ELA shows an ascending trend. Data analysis shows when net ablation increased 10×10⁴ m³, ELA would ascend 14 m. Analytical results of the ELA sensitivity response to climate change suggest that every 1 ℃ summer temperature increase would lead to 82 m ELA ascendance, and ELA would descend 41 m when annual precipitation increased 100 mm. According to the difference of ELA sensitivity in response to summer temperature and precipitation, ELA ascendance was controlled mainly by summer temperature.