In this paper, the Huangfuchuan Watershed was chosen as the study area, and RS and GIS techniques were used to explore the land use change and NPP. With the combination of CASA model, the dynamic characteristics of NPP in 1987—2011 were studied. Land use structure changed obviously in the Huangfuchuan Watershed. The main trend of land use change was the gradual increase of construction land and woodland as well as the gradual decrease of water. The areas of arable land, grass, shrub, bare rock and sand were fluctuant, as shown by land use dynamic degree. The calculation of NPP model shows that the total value of NPP in 1987, 1995, 2000, 2007 and 2011 was 28. 12 GgC, 53. 47 GgC, 73. 23 GgC, 157. 92 GgC and 78. 52 GgC. The analysis of land use change effects on NPP indicates that the main factor responsible for the increase of NPP was the transformation of the grassland to the shrub between 1987 and 1995 , whereas the bare rock was the main factor responsible for the increase of NPP in 1995—2000 . The change of shrub into grassland contributed mainly to the increase of NPP in 2000—2007 , whereas the change of grassland into shrub contributed mainly to the reduction of NPP in 2007—2011 . The results of the study is of great significance for rational utilization of temperate grassland resources and improvement of the fragile ecological environment.%以皇甫川流域为研究区域,定量分析皇甫川流域土地利用变化,采用光能利用率模型,研究1987年、1995年、2000年、2007年和2011年7月份皇甫川流域植被净第一性生产力( net primary productivity,NPP)的动态变化。结果表明：研究区建设用地、林地面积逐渐增加,水域面积逐渐减小,耕地、草地、灌丛、裸岩和沙地呈波动变化；5个时期皇甫川流域NPP总量分别为28.12 GgC,53.47 GgC,73.23 GgC,157.92 GgC和78.52 GgC；1987—1995年间,草地转移为灌丛是NPP增加的主要原因；1995—2000年间,裸岩减少是NPP增加的主要原因；2000—2007年间,灌丛转移为草地是NPP增加的主要原因；2007—2011年间,草地转移为灌丛是NPP减少的主要原因。研究结果对温带草原系统土地资源合理利用、土地利用结构优化、脆弱生态环境改善具有重要的理论与实践意义。
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