Ephemeral gully development (EGD) drives substantial land degradation, profoundly altering soil erodibility properties in cropland. Despite its importance, the spatial patterns of soil erodibility properties within degraded areas, as well as the underlying controlling factors, remain poorly understood. This study quantitatively assessed the spatial heterogeneity of eight soil erodibility indicators in cropland degraded by EGD in the Mollisol region of Northeast China. An improved construction procedure based on network analysis was employed to integrate these indicators into a comprehensive soil erodibility index (CSEINA), while the dominant factors and underlying pathways governing the index were identified. The results indicated that structural stability index, penetration resistance, soil cohesion, mean number of raindrop impacts and mean weight diameter progressively decreased from original cropland to gully floor, with average decreases ranging from 2.6% to 12.0%. From contribution area to lower slope, these indicators followed a decrease-increase pattern, with variation ranges of -43.4% to -4.9% and 10.3% to 117.3%. In contrast, erodibility factor, saturated hydraulic conductivity and slaking rate exhibited opposite trends. CSEINA provided a more effective characterization of soil erodibility and better captured its spatial variability. In the ephemeral gully system, the CSEINA peaked at the gully floor and middle slope, which should be prioritized for erosion risk management. Clay content, sand content, physical crust thickness, organic matter content, root mass density, and straw mass density were identified as the dominant factors influencing CSEINA, jointly explaining 92.5% of its variability. These findings offer essential theoretical and methodological insights for managing soil erodibility in erosion-degraded cropland.