Vegetation cover and its dynamic changes could effectively reflect the characteristics of regional environmental changes. Monitoring vegetation changes was an indispensable part of evaluating the ecological environment quality of the region. The data source of this paper adopts Landsat remote sensing image, based on the normalize difference vegetation index and dimidiate pixel model to calculate the vegetation coverage of the surface water source field of the Laolongkou Reservoir in Hunchun in 2002, 2009 and 2018, and carry out the analysis of dynamic change. The results show that the average vegetation coverage value of the surface water source area of Laolongkou Reservoir in Hunchun from 2002 to 2018 increased after decreasing, the overall vegetation coverage in this area was relatively good between 2009 and 2018, with the medium height and high-vegetation coverage areas accounting for 86.99% of the total area. In terms of space, the vegetation coverage in the northeast of the surface water source is high, and it decreased from east to west. The high vegetation coverage area has changed significantly, with an increase of 1818.80km2 in the past 20 years. Government policies, ecological restoration projects, and human activities are the main factors affecting the vegetation coverage of surface water sources of the Laolongkou Reservoir in Hunchun.