A prediction of snow cover depth change in northern Xinjiang in the next 50 a is made used by GCM simulation, which joins the Coupled Model Intercomparison Project ( CMIP3) . Firstly, the snow cover data observed and simulated by 20C3M during 1961- 2000 are analyzed and compared, and then the performance of the models in snow cover is examined. Because of the effects of terrains,desert and arid climate environment in northern Xinjiang, as well as the resolution of GCM, the performance of GCM is limited. Secondly, based on the inspecting of significance of correlation and root mean squire, INM-CM3. 0 and CGCM-T47_1 are chosen to predict the snow cover in the next 50 a over northern Xinjiang. Further, the distribution features of snow cover over northern Xinjiang in the last 40 years were analyzed. It is found that,during 2002- 2050, in A1B and B1 scenarios, on whole, the snow cover depth will appear a decrease tendency , however, there will be some difference in the decrease in snow co ver depth in the south Altay Mountains. In A2 scenarios, the results simulated by INM-CM3. 0 and CGCM-T47_1 have a relative large difference in snow cover variations in Junggar basin.