[Objective] The dynamic changes of vegetation and its response relationship with topography in Changbai Mountain were explored in order to provide scientific support for ecological environmental protection and management in this mountainous area.[Methods] Based on MODIS NDVI and DEM data, fractional vegetation cover in Changbai Mountain from 2000 to 2020 was estimated using a pixel dichotomy model. Spatiotemporal variations of fractional vegetation cover were analyzed in depth using Sen+Mann-Kendall trend analysis, spatial autocorrelation analysis, and a center of gravity migration model. At the same time, the differential effects of vegetation cover variations were quantitatively determined by combining the analysis results with the correction coefficient for topographic areas in this study in terms of elevation, slope, and aspect factors.[Results] ① In terms of spatiotemporal distribution, the fractional vegetation cover in Changbai Mountain increased at a rate of 0.023 7/10 yr (p<0.001) from 2000 to 2020 and underwent an obvious upward mutation in 2010, showing a distribution pattern of "high around and low in the middle", with an overall level of high. ② In terms of spatiotemporal variation, the area of vegetation improvement in Changbai Mountain was much larger than the area of degradation from 2000 to 2020, showing a significant clustering state dominated by a "high-high" pattern. However, the degree of clustering showed a fluctuating downward trend, and the center of gravity of vegetation cover generally migrated to the southwest during the 21-yr study period. ③ In terms of topographic differentiation, the fractional vegetation cover in Changbai Mountain increased and then decreased with the increase of elevation and slope over time. During different time periods, vegetation in the areas of elevation <600 m, ≥ 1200 m and slope <2°, ≥ 25° generally showed a degradation trend. The areas primarily showing improvement or stabilization over time had elevations of 600-1 200 m and slopes of 2°-25°. The trend of vegetation degradation was obvious in the flat land area, while little difference in the variation types was observed for other aspects.[Conclusion] The vegetation condition of Changbai Mountain has generally improved over the past 21 years. Spatial differentiation of vegetation variations under different elevations and slopes was obvious, while the effect of aspect on vegetation variations was not significant.