Context As a dominant factor influencing soil erosion, soil aggregate stability is likely to be closely associated with land use and soil parent material in the red soil region of southern China. However, few studies have comprehensively examined how land use and soil parent material jointly influence the stability of soil aggregates.Aim This study aimed to evaluate the synergistic impact of land use and soil parent material on soil aggregate stability.Method Soil samples were collected from 0-100 cm depth across four typical land uses (natural forests, artificial forests, orchards, and sloping farmland) and two parent materials (granite and slate). Soil aggregate stability was assessed using a new approach of vector method to calculate the vector length stability index (VLSI) and its weighted form (wVLSI).Key results Soil aggregate stability was highly linked to land use. When natural forests were converted to orchards and sloping farmland, VLSI and wVLSI decreased significantly in most cases (P < 0.05). In contrast, VLSI and wVLSI increased significantly in granite soils after conversion to artificial forests (P < 0.05). Soil parent material also exerted substantial influence on soil aggregate stability, and the slate soil had greater capacity to resist flowing water erosion than did granite soil. General linear model analysis showed that the effect of land use on soil aggregate stability was greater than that of soil parent material. The wVLSI demonstrated greater effectiveness than VLSI in evaluating soil aggregate stability across different land uses and soil parent materials.Conclusions The vector method can effectively discriminate soil aggregate stability under different land uses and soil parent materials.Implications Due to its efficient and simple experimental procedure, the vector method is recommended as a practical and useful approach for future studies.