Based on MODIS10A2 snow cover data from 2001 to 2015,the MODIS10A2 500 m resolution data were preprocessed through geometric correction and cloud effects elimination. The snow-cover area was extracted using normalized difference snow index (NDIS) algorithm and the comprehensive threshold discriminator in combination of DEM data and the temporal and spatial distribution characteristics of the snow cover in the Tianshan Mountains in China were analyzed. The results indicated as follows : (1) During the time period from 2001 to 2015, the snow cover area of Tianshan Mountains showed a decreasing trend and it was decreased by 0.27 * 10~4 km~2 from 2001 to 2015. It showed a single peak distribution during a year with the peak in January and the least in July. The snow cover area in summer is small and its change rate year after year is also small. The snow cover area in winter is the biggest and it shows a downward trend year after year with an average annual decrease rate of 823 km~2. (2) The maximum and minimum snow cover areas in Tianshan Mountain were calculated systematically. The year with the largest snow cover area was 2003 and the smallest,2007. The maximum snow coverage ratio ranges from 75% to 53% and it happened in December and January timeframe. The minimum ratio ranges from 1% to 4% which occurred in July and October timeframe. The fluctuation on the maximum snow coverage was more intense than that on the minimum. (3) The snow coverage ratio is increased gradually along the altitude with a value less than 10% below 1 500 m and a value of 70% above 4 500 m. The snow coverage ratio was changed with slope. It was higher in northwest,west,north and northeast slopes than in the southwest,south and southeast slopes. It was 25% on the northwest slope, 16% on the south slope. (4) In recent years,Tianshan Mountain area has shown a temperature rising trend. The correlation analysis demonstrated that the snow coverage,which is sensitive to climatic factors,and had a significant negative correlation (R = 0.17) with the air temperature but was less relevant to the precipitation. Temperature rising is the main cause for the decrease of snow cover area. The annual snow cover area change showed a similar trend to the annual precipitation change,both were on a declining curve.