In recent years, research on the relationship between the Normalized Difference Vegetation Index (NDVI) and climate factors has gained significant interest. This study examines vegetation changes in different forest ecosystems in China using the NDVI dataset from 1998 to 2015 and corresponding climate factor data (temperature and precipitation). Trend line analysis and correlation analysis methods are employed to investigate the spatial and temporal change characteristics of NDVI in five representative Chinese forest ecosystems. The driving forces of the two climate factors are simultaneously analyzed. The results indicate that: (1) Over the 18-year study period, the annual maximum NDVI of China’s forest ecosystems exhibited a significant increasing trend (P<0.01), with an average annual increase of 0.0043; (2) Vegetation cover changes demonstrated an overall upward trend, with the NDVI of 84.87% of the forest vegetation in the study area increasing. However, a minimal decrease was observed in 0.94% of the study area; (3) Vegetation coverage in China’s forest ecosystems has increased over the past 18 years, exhibiting a greening trend. Across the entire study area, the correlations between NDVI and temperature and precipitation were insignificant.