Rocky desertification is a major ecological problem in karst regions, driven by the combined effects of natural conditions and human activities. To investigate its spatiotemporal evolution and driving mechanisms, this study constructed a two-dimensional Rocky Desertification Index (RDI) based on the Normalized Difference Vegetation Index (NDVI) and Bare Land Index (BLI) for Liupanshui City, Guizhou Province, China, during 1987-2022. The results showed that the overall classification accuracy reached 88.16%, and rocky desertification exhibited an overall alleviation trend, with non-desertified areas expanding continuously and moderate and intensive rocky desertification decreasing significantly. Optimal Parameter-based Geographical Detector (OPGD) analysis identified land use as the dominant driving factor, with q-values ranging from 0.44 to 0.64, while its interactions with climatic and terrain factors showed enhanced explanatory power. Partial Least Squares Structural Equation Modeling (PLS-SEM) further revealed a clear shift in driving mechanisms, from natural-factor dominance before 2000 to increasing human-activity dominance after 2007. These findings provide scientific support for rocky desertification control and ecological restoration in karst regions.