Abstract: This study aims to determine the impacts of human activities on the ecosystems of Henan national nature reserves in an objective, timely, and accurate manner, so that problems existent in management and protection can be identified and evaluated in time. Based on Chinese high-resolution remote sensing images from 2016 to 2018, this study extracted data on land cover types of national nature reserves in 2016 and human activities in 2016, 2017, and 2018. Then, the source, change type, distribution pattern, and temporal-spatial transformation of new human activities in the reserves were ascertained using the transition matrix. Furthermore, the changing characteristics of human activities in different types of reserves were analyzed. Finally, the impact degree and change patterns of human activities on the reserves were evaluated using the impact intensity index of human activities. The results are as follows. Human activities dominated by agricultural land and residential areas were widespread in Henan national nature reserves in 2016. They were mainly distributed in inland wetlands and paleontological relic reserves. From 2016 to 2018, new human activities were mainly distributed in inland wetland reserves, which were mainly transformed from agricultural land, forest land, grassland, and wetland. From 2016 to 2018, the human activities in the reserves had an impact intensity index range of 0.045~4.735. The impact degrees of human activities on reserves of forest ecological type, inland wetland type, wildlife type, and Paleozoic relic type were slight, significant, general, and severe, respectively. Therefore, the spatial distribution, types, intensity, and dynamic changes of human activities in the reserves can be accurately identified using the remote sensing technology and the impact intensity assessment model. This study can be used as an important guide for scientific assessment and improvement of the management of the reserves.