Actual net primary production (ANPP) is affected by both natural conditions and human activities in many areas, while the contributions of these factors to NPP remain unknown because it is difficult to isolate their effects. This knowledge gap hinders our implementation of environmental protection and restoration. In this study, we selected three basins of the Hexi Corridor, North‐western China, as the study area. Based on the monthly growth of grassland and field observations, we identified the undisturbed grids and then calculated the potential net primary productivity (PNPP) of these grids. Using the Carnegie‐Ames‐Stanford‐Approach (CASA) model, we calculated the ANPP in these areas. The influence of human activities on NPP (HNPP) was then calculated as the difference between ANPP and PNPP. The results showed that from 2001 to 2017, the mean grassland HNPP was −236.25 gC m−2 a−1. The area with a relative contribution index (RCI) of human activity greater than 0.5 accounted for more than 50% of the total, indicating that human activities were a dominant factor in the NPP change. After the implementation of ecological governance projects in the Hexi Corridor in 2006, HNPP exhibited a negative weakening rate of 2.79 gC m−2 a−1 (p < 0.05), and the RCI decreased from 0.708 at the beginning of the study period to 0.522 at the end (p < 0.01), indicating that reducing human interference with nature was an effective measure for ecological restoration. Based on these findings, we concluded that the changes in NPP in the three basins of the Hexi Corridor was dominated by human activities. Our results suggest that future studies pertaining to the response of NPP to climate change should consider the impact of human activities in semi‐arid regions.