As a critical surface cover in terrestrial ecosystems, biological soil crusts (biocrusts) significantly decline soil erodibility through direct surface protection, including covering the soil surface and binding soil particles, and indirect improvement of soil structure. Nevertheless, linkages between soil erodibility variation and biocrusts development as well as the underlying mechanisms remain poorly understood. Thus, this research was conducted to quantify the temporal variation in soil erodibility and elucidate the coupling mechanisms between biocrusts development and variation in soil erodibility for biocrusts with different (high, medium, and low) coverage gradients in the Three Gorges Reservoir area (TGRA). A comprehensive soil erodibility index (CSEI) derived from eight soil erodibility indicators was applied to assess soil erodibility in the current study. The result showed that CSEI exhibited a distinct temporal pattern: it decreased gradually from January to May, then increased fluctuating to the peak in September, before decreasing rapidly from September to November. Compared to CSEI in January, CSEI in November declined by 24.77%, 19.06%, and 14.23% for high, medium, and low coverage gradients, respectively, demonstrating that the development of biocrusts substantially reduced soil erodibility. Temporal variation in CSEI was closely associated with the changes in biocrusts growth characteristics and the subsequent shifts in soil particle distribution and structure. Notably, their influencing mechanisms exhibited notable disparities across different biocrusts coverage gradients. The PLS-SEM result demonstrated that for biocrusts with high and low coverage gradients, temporal variation in soil erodibility was governed by the direct physical effects of biocrusts (e.g., particle binding), whereas that for medium coverage gradient was predominantly controlled by its indirect effect in improving soil structure. These findings advance understanding of biocrust-mediated soil stability and support targeted land management of fruit forest in the TGRA.