[Objective] To analyze the mechanisms of vegetation degradation and stability maintenance during the process of desertification at the southeastern edge of Mu Us sandy land, and to provide scientific basis for the repairing and controlling of desertification.[Methods] The methods of field investigation, field sampling, indoor assay and statistical analysis were integrated to analyze the change of vegetation characteristics during desertification in the study area.[Results] The results of functional and structural characteristics showed that the vegetation coverage, density, richness and Simpson diversity index reduced; The aboveground biomass increased first and then decreased. The changing regularity of organic matter was not obvious, while the total nitrogen content decreased and C/N increased. Vegetation characteristics changed suddenly in the mild desertification stage which was the key stage for desertification repairing. Furthermore, the quantitative measurement of vegetation stability showed that the stability index decreased in the process of desertification, stable and basically stable in non-desertification stage and potential desertification stage, unstable in other stages.[Conclusion] The vegetation degrades and the stability indexes decrease with desertification deepens. Therefore, maintain the virtuous circle of plant-soil system is the key of vegetation restoration and desertification control.