Based on monthly mean ERA-Interim reanalysis data and the temperature and precipitation data in the arid area of Northwest China during 1979-2013, differences in climate in the arid area of Northwest China between strong and weak monsoon years are analyzed. Correlation between the plateau monsoon and climate in the arid area of Northwest China is quantified. The mean large-scale circulation and water vapor transport are compared between strong and weak plateau monsoon years. The results show that the correlation between the plateau monsoon and climate in the arid area of Northwest China is significant. There are obvious differences in large scale circulation and vertical circulation system between the strong and weak monsoon years. The water vapor condition and uplifting condition are in good agreement with precipitation. The ability of water vapor uplifting along the northern flank of the Plateau is one of the important factors affecting climate in the arid area of Northwest China.