Vegetation cover is affected by climatic factors and human activities interactively,and temperature and precipitation are typically known as the most important climatic factors.Path analysis was applied to analyze the effects of climatic factors on vegetation cover and net primary production(NPP)of different climatic zones in the Loess Plateau for the recent 15 years based on the MODIS data (MOD44B, MOD17A3)and meteorological data(temperature and precipitation).The results showed that:(1)Vegetation cover fluctuated with a insignificant rising trend(r=0.467,P>0.05)from 2000 to 2014 in the Loess Plateau.The tree cover increased significantly(r=0.864,P<0.01),with 40.56%of the total area of the Loess Plateau experiencing an highly significant increase,mainly distributes in north Shaanxi and Luliang Mountain Range.The tree cover with an insignificant increasing trend accounted for 41.68%area of the Loess Plateau.(2)In the semiarid Loess Plateau,precipitation had a higher impact on the tree cover than temperature did.It also increased vegetation cover,tree cover and NPP in different climatic zones significantly. Moreover,NPP was much more sensitive to precipitation variations under cold and drought circumstances.(3)NPP can be affected by temperature and precipitation directly,and indirectly through changes in vegetation cover.The tree cover imposed higher influence on NPP than non-tree cover did,and climatic factors had a stronger indirect effect on NPP in rainy area.