Abstract: Abstract: Background Soil erosion threatens ecological security and alters key ecosystem processes. Sediment connectivity serves as a vital tool for quantifying sediment transport efficiency and supporting soil and water conservation decision-making. However, existing research lacks systematic comparisons of the representational performance of different connectivity indices, and quantitative analyses of the contributions of key drivers, such as vegetation and rainfall, over long-term series remains insufficient. Therefore, this study aimed to evaluate the impacts of vegetation coverage and rainfall erosivity on sediment connectivity in the Longchuan River Basin and to identify the index that best represents sediment transport rate potential. Methods This study was based on a 35-year dataset (1986-2020) from the Longchuan River Basin. Three sediment connectivity indices were employed: the sediment connectivity index (IC) based on the cover-management factor (C), the IC_R index based on rainfall erosivity (R), and a revised sediment connectivity index (ICr) coupling both factors. Regression analysis and spatial correlation analyses were used to clarify the impacts of vegetation coverage and rainfall erosivity on sediment connectivity. The relative contributions of vegetation coverage and R to changes in ICr were quantified using Lindeman-Merenda-Gold (LMG) analysis. Correlations between each index and measured sediment transport rates were analyzed to evaluate their representational performance. Results (1) During the study period, the Normalized Difference Vegetation Index (NDVI) of the basin exhibited a significant increasing trend, while the IC index showed a significant decreasing trend. A highly significant negative correlation was observed between their temporal variations (R2 = 0.99), indicating that the improvement in vegetation cover can effectively reduce sediment connectivity in the basin. Spatially, Vegetation coverage was relatively lower in the northeastern part of the basin, where IC values were correspondingly higher. Spatial correlation analysis further revealed a negative correlation between vegetation coverage and IC. (2) Both the IC_R index and rainfall erosivity (R) displayed pronounced inter-annual fluctuations without a significant long-term trend, and they showed strong positive correlations in both temporal and spatial dimensions. (3) The ICr index demonstrated a significant decreasing trend, indicating an overall improvement in sediment connectivity in the basin. Its variation was primarily controlled by vegetation coverage, which accounted for 97.10% of the contribution, while rainfall erosivity contributed 2.90%. (4) Both the annual average and annual maximum sediment transport rates in the basin exhibited significant decreasing trends. The correlation coefficients between the ICr index and the annual average sediment transport rate (r = 0.55), as well as the annual maximum sediment transport rate (r = 0.39), were higher than those obtained using the IC and IC_R indices. Conclusions This study successfully achieved its predefined objectives. At the inter-annual scale, vegetation restoration is the dominant factor inhibiting sediment connectivity and reducing transport potential in the Longchuan River Basin, whereas rainfall erosivity mainly acts as a driver of inter-annual variability without forming a long-term trend. Among the three indices, the ICr index, which simultaneously considers the inhibitory effect of vegetation and the driving effect of rainfall, more accurately represents the actual sediment transport potential of the basin. These findings provide a quantitative basis for targeted soil erosion prevention and control in mountainous regions of Southwest China.