Land desertification has been one of the hot issues of global concern. In this paper, the typical area of Horqin grassland, Horqin Left Wing Rear Banner, is selected as the study area, and based on the land use data from 1986 to 2021, the desert land is classified by vegetation cover to explore the spatial and temporal variations of land desertification in the region and its underlying driving mechanisms using principal component analysis, and the intrinsic driving mechanism is explored. The results show that, (1) In the last 35 years, the area of desertified land in the study area has been increasing and decreasing, with a general trend of reversal. In terms of the degree of desertification, the formation gradually decreases from west to east. (2) The total area of desertified land decreased by 20.78%. Among them, there was a gradual decrease in the area of land subject to mild desertification from 12.12% to 8.67%, mainly in the eastern part of the study area; and the area of moderately desertified land decreased from 54.08% to 32.95%, which was distributed in the central and northern parts of the area; the area of heavily desertified land showed a trend of increasing and then decreasing, firstly from 12.33% to 34.51%, and then later on decreased to 16.13%, mainly in the western part of the study area. (3) The evolution of desertified land in the study area is mainly influenced by anthropogenic factors, with natural factors playing a secondary role. The contribution of anthropogenic factors in the principal component analysis is significantly higher than that of natural factors, with the contribution of the first principal component of anthropogenic factors such as arable land area, livestock volume, and GDP being 0.961, 0.898, and 0.896, respectively, and the contribution of the total population at the end of the year in the second principal component being 0.746. Therefore, in the process of desertification control, policies such as the grazing ban and grazing rest should be implemented effectively, and sand control and sand prevention projects should be carried out reasonably, which is conducive to further reducing the degree of desertification and can provide a solid foundation for the construction of the northern ecological barrier in China.