Net primary productivity (NPP) is one of the important parameters for assessing global ecosystem stability and ecological safety, and changes to NPP distribution directly affect regional ecological function and natural environment evolution. Our study area forms part of the Yili River Valley and Tianshan Mountains in Xinjiang, China. Through analysis of mathematical statistics datasets composed of NPP, climate and meteorology, soil, and plant and elevation we found that: (1) the dominant factors for NPP in arid areas of middle latitude were moisture and elevation; (2) correlation analysis indicated that the annual average temperature, annual average precipitation, aridity, humidity index, elevation, and slope showed significant correlation with NPP (P<0.01) and, additionally, there were some correlations among the environmental factors; (3) under different environmental temperatures, the effect of the driving ability of the environmental factors on NPP was different: when the average annual temperature was below 0 ℃, NPP was driven by elevation (P<0.01); when it was above 0 ℃, NPP was driven by moisture factors (P<0.01); (4) there were significant differences in NPP driving factors between different vegetation and soil types; (5) the NPP value first increased, and then decreased with rising altitude, and altitude had a decisive effect on the driving characteristics of NPP environmental factors. Based on the above conclusions, we revealed the important influence of altitude and the effects of environmental factors on NPP in arid areas of mid-latitudes. Furthermore, the effects of the driving force of altitude on NPP needs further exploration.