Land desertification constitutes a critical global ecological challenge. In China, desertification areas cover approximately 27% of the national landmass. Continuously conducting monitoring and research on land desertification is of great significance for promoting ecological restoration in desertification areas. Addressing limitations of NDVI-Albedo feature space extraction, this study integrates comparative model analysis to propose a remote sensing extraction method for land desertification in alpine meadow areas based on the OSAVI-Albedo feature space. We developed an OSAVI-Albedo feature space framework to derive temporal desertification differential index (DDI) for Shangri-La city, and conducted a spatio-temporal dynamic monitoring study of land desertification in the study area over the past 20 years, and the distribution and change patterns of regional land desertification were identified. It also explores the impact mechanisms of natural and anthropogenic factors on the evolution of regional desertification by combining local meteorological and demographic data changes. The results show that the OSAVI-Albedo model can effectively overcome the shortcomings of the NDVI-Albedo model, such as oversaturation and outliers, and differentiate surface vegetation coverage without interference from special ground objects. From 2003 to 2022, Shangri-La's desertification showed improvement: the area of mild/moderate/severe categories decreased by 30.3%, 34.6%, and 14.3% respectively. Meanwhile, the area of non (no) and potential categories increased by 27.9% and 3.9% respectively. The area where desertification improves is approximately four times larger than the area where it has deteriorated, and the area where desertification is showing a decreasing trend is twice as large as the area where it is aggravated. Only some local areas experienced desertification deterioration and fluctuation. Multivariate analysis reveals three key drivers affecting the evolution of regional land desertification: bioclimatic factors (temperature/precipitation), anthropogenic pressures (land use change/population density), and restoration initiatives (including Grain-for-Green Program, Grazing Ban Policy, Natural Forest Conservation Project, and Forest Ecological Compensation mechanisms). Among them, bioclimatic factors are influenced and constrained by topography and altitude. Bioclimatic factors show different correlation characteristics with desertification under different topography and altitudes. The impact of human activities on desertification is manifested in multiple aspects: firstly, the increase in population density exacerbates the development of the natural environment, leading to an exacerbation of land desertification; secondly, the direct transformation of land use by human activities can quickly cause changes in vegetation cover, leading to rapid improvement or deterioration of desertification; lastly, through the implementation of restoration initiatives, the ecological environment has been well protected and restored, and the trend of land desertification has been effectively suppressed.