In this paper, the daily datasets of snow depth, mean air temperature, and precipitation from 104 meteorological stations and NCEP/NCAR were used to study the snow cover days in winter in the arid region of Northwest China during 1961- 2010. K- means clustering, Mann-Kendall test and other methods were used to calculate the temporal- spatial characteristics of the snow cover days and interpret the reason of the climate change. The results indicated that: 1) More snow cover days in winter mainly distributed in Junggar Basin and Altai Mountains (i.e. the region of III). The snow cover days in winter decreased gradually from high latitude to low latitude in the Inner Mongolia Plateau (i.e. the region of I). The snow cover days in winter were relatively few in the Xiliao River Basin, Ordos Plateau, Alxa Plateau, Tianshan Mountains and Tarim Basin (i.e. the region of II). 2) During the period 1961-2010, the snow cover days in winter presented an increased trend in the arid region of Northwest China, and the abrupt change was found in 1984. The big change of snow cover days in winter happened at some meteorological stations in the Inner Mongolia Plateau (i.e. the region of I), while snow cover days in winter had no obvious change at the stations in the Xiliao River Basin, Ordos Plateau, Alxa Plateau, Tianshan Mountains, Tarim Basin, Junggar Basin and Altai Mountains (i.e. the regions of II and III). 3) The variation of snow cover days in winter showed the periods of 5 years, 10 years, 25 years, approximately. The period of 25 years showed the most significance. 4) The increased precipitation in winter, caused by the weaken the East Asia major trough and Southern branch trough and the enhancement of the westerly wind, maybe the main factor of the increased trend of the snow cover days in winter in the arid region of Northwest China.