Water resources,a key factor,restricted economic and social development and ecological security in arid region of Northwest China.The water resources in arid area mainly come from snow melt water and mountain precipitation.Therefore,studies on the impact of climate on snow cover and runoff in arid region of Northwest China have a significant impact on the water resources management,ecological protection,and economic and social development.Based on MODIS data,the meteorological and hydrologic station data,the present investigation was conducted to analyze the trends of annual snow cover and streamflow variations in the Kaidu River and discuss the relationship between climate change,snow cover,and streamflow.We used Mann-Kendall test,Pearson correlational analysis method,and sensitivity analysis.We found that the total snow cover fraction showed a slightly increasing trend from 2000 to 2016 (-0.017%/a).The annual maximum snow cover increased but the annual minimum snow cover exhibited a decreasing trend.Seasonally,the snow cover decreased in spring and summer,increased in autumn and winter.In the past 45 years (1972-2016),the onset of snowmelt period documented a shift of 10.35 days earlier while ending date did move 7.56 days later.The correlation between snow cover and meteorological variables suggest that the snow cover was mostly affected by temperature in spring and was mostly influenced by precipitation in winter.Both the annual streamflow and peak streamflow exhibited an increasing trend from 2000 to 2016 in a speed of 226 million m~3 per decade.The streamflow is sensitive to the variations of temperature and precipitation in summer,and to the variations of snow cover in spring.Increasing of temperature and precipitation is the primary factor leading the increasing of streamflow.