Abstract: The snow reserves in Deqin County is an important freshwater resources and dominates in runoff recharge and water resources pressure allevation in the three parallel rivers region. This paper uses NDSI index to extract the snow cover information of Deqin County in 1989,1996,2000,2009 and 2015 based on 10 scenes of TM, ETM +, OLI images, DEM and meteorological data and analyses the spatial and temporal variation characteristics of snow cover area and the relationship between the changes of snow cover and climate. The results show that the snow area showed a decline trend year by year, decreased from 819.8847 km2 to 619.1154 km2 in 26 years, accounting for 24.5% of the total, with yearly reduction of 7.44 km2; the snow areas in different altitude zones all reduced and the most quick and obvious in the zones of 1464～3000 m, comparably quick in the zone of 3001～4000 m; the snow cover distributed in the altitude of 4001～6740 m reduced most slowly. The increasing temperature and decreasing precipitation accelerated the shrinkage of snow cover area in recent 26 years.