【Objective】Coal gangue dumps are commonly reclaimed through topsoil covering and artificial planting, yet stable vegetation remains difficult to establish in some reclaimed areas. Identifying the associated constraints is essential for facilitating ecological restoration. 【Method】Four coal gangue dumps reclaimed in 1990, 2005, 2012, and 2018 in Yangquan, Shanxi Province, were investigated. Well-vegetated and revegetation-limited sites within each dump were sampled in pairs. Topsoil physicochemical properties, structural stability, enzyme activities, bacterial abundance, and community composition were analyzed. Response ratios, grouped Mantel tests, and partial least squares path modeling (PLS-PM) were used to identify stable indicators and potential pathways of vegetation limitation. 【Result】Sulfur accumulation and insufficient water and nutrient supply were the most prominent characteristics of vegetation-limited topsoil. In the revegetation-limited sites of the four reclamation years, total sulfur contents were 2.40, 3.63, 5.08, and 7.65 g?kg?1, and sulfate sulfur contents were 337.2, 528.8, 863.7, and 1 947 mg?kg?1, respectively. Bulk density in well-vegetated sites was significantly lower than that in revegetation-limited sites across all four reclamation years, indicating higher structural stability. Enzyme activities and bacterial alpha diversity showed unstable response directions, whereas 16S rRNA gene copy numbers were significantly higher in well-vegetated sites than in revegetation-limited sites across all four reclamation years, indicating that bacterial abundance showed a stable response to revegetation-status differentiation. Micrococcaceae was the dominant taxon in all sites. Principal coordinates analysis (PCoA) and permutational multivariate analysis of variance (PERMANOVA) showed significant differentiation in bacterial community structure. Bacterial Bray-Curtis dissimilarity was most strongly correlated with sulfur-salinity constraints. Sulfur-salinity constraints had significant negative effects on water supply, nutrient supply, structural stability, and bacterial response. The PLS-PM further revealed correlations among topsoil limiting factors. 【Conclusion】Sulfur-salinity accumulation, structural compaction, insufficient water and nutrient supply, and reduced bacterial abundance jointly formed the topsoil barrier to revegetation establishment. Total sulfur, sulfate sulfur, bulk density, and 16S rRNA gene copy number can serve as priority diagnostic indicators. These findings provide a scientific basis for topsoil quality diagnosis and ecological restoration of coal gangue dumps.