Abstract:[Objective] To Explore the effect of land use/cover change on the net primary productivity(NPP) in grassland ecosystem of Ordos City in order to provide theoretical basis for the efficient implementation of grassland grazing mitigation measures and the reasonable management of grassland resources.[Methods] Based on multi-source remote sensing image data, multi-period land use/cover data and meteorological data, using Carnegie Ames Stanford Approach(CASA), the NPP of grassland ecosystem was simulated and the land use change was demonstrated. Upon which, the impact of land use/cover change(LUCC) on grassland NPP in Ordos City was analyzed.[Results] ① The grassland NPP in Ordos City increased gradually from 5 700.16 Tg in 2001 to 7 634.61 Tg in 2015. There existed significant regional difference in NPP spatial distribution. ② From 2001 to 2015, the area of arable land continued to decrease. While, the area of forest increased, with a total increase of 4 593 km2. The net reduction of grassland area was 786.38 km2. For the mutual land use conversion, the one between grassland and unutilized land was the largest. And also there were a large amount of arable land and the woodland, with total area of 376.5 km2, were converted into grassland. In contrast, the largest decreasing in grassland that was converted to unutilized land was 1 211.50 km2. ③ From 2001 to 2015, the NPP increased by 1 999.42 Tg in grassland covered area. The changes of grassland to other types of land led to a NPP reduction of 303.98 Tg. Among of them, the conversions to cultivated land, forest and unused land accounted for 35.08 Tg, 69.81 Tg and 118.28 Tg, respectively. Additionally, the conversion of other types of land to grassland resulted to an increase of NPP, totaled to 128.96 Tg. The increments of grassland NPP from farmland, forestland and water were 36.30, 31.39 and 17.58 Tg, respectively.[Conclusion] Land use/cover has a greater impact on grassland NPP. Conversions of cultivated land and forest to grassland and reuse of unused land all increased grassland carbon sink. The conversions of grassland to unutilized land, water areas, and urban-rural residents' land for industrial and mining uses could all weaken carbon sinks of grassland ecosystem.