Monitoring the spatiotemporal variation of snow cover in Tianshan Mountains is very important for fully utilizing water resources and understanding the effects of climate change at regional levels.In this paper,the cloud removal methodology based on cubic spline interpolation is used to removed cloud from the MODIS daily fractional snow cover data.Based the cloud removed MODISdaily fractional snow cover data, the spatiotemporal changes of snow cover during 2001to 2015in Tianshan Mountainswere examined.Theresult s show thatthe snow cover accumulates from September and start melts in February.The snow cover extent reaches the maximum value(more than 60%)in late January,and the minimum value(about 1.5%)in July and August.Thesnow cover of spring,summer and autumn in central Tianshan is significantly higher than in other regions,but he highest snow cover in winter is located in thenorthern Tianshan. There is a strong interannual variability of snow cover in the 15years.The average snow cover of summer and winter in the study area shows a decreasing trend,while it shows an increasing trend at spring and autumn. The snow covered days(SCD)in 26.39%of the study area presents a decreasing trend(5.09% with a significant decrease).The areas with significant decrease in SCD are mainly located in centralTianshan and the east part of easternTianshan.34.26%of the study area shows a increasing trend(2.8% with a significant increase)in SCD.The areas with SCD significant increased are mainly located in northern Tianshan and west part of easternTianshan.