Abstract: This study was aimed to quantitatively analyze the effects of rainfall characteristics, vegetation and level ditch on soil erosion in the understory of Pinus massoniana forests, and to meet the new demands for optimizing the utilization of forest land resources in line with regional characteristic industrial development. An in-situ field experiment on runoff in the typical distribution area of Pinus massoniana was conducted in Jiangxi Province. Four runoff plots were set up: Pinus massoniana + cleaning tillage under the forest (MLD), Pinus massoniana + Ilex asprella (MG), Pinus massoniana + Ilex asprella + level ditch (MGZ), and bare land(LD). The study aimed to investigate the effects of erosion factors (rainfall characteristics, vegetation and level ditch) on surface runoff and soil erosion under successive rainfall. The K-means clustering method identified three typical rainfall patterns in the red soil area: RⅠ, RⅡ, and RⅢ. Among them, the RⅢ pattern (low frequency, large rainfall amount, long duration, large I₃₀) is the most significant rainfall pattern causing regional soil erosion, accounting for 77.54% of the runoff volume and 73.09% of the sediment yield. The combined influence of rainfall characteristics, vegetation, and level ditches on surface runoff and sediment transport can explain 61.3% of the total variation in slope runoff and sediment transport. The explanatory capabilities of rainfall characteristics, vegetation, and level ditches, with contribution rates of 53.5%, 33.7%, and 12.8% respectively. The sediment reduction effect of the Pinus massoniana forest plot (MLD, MG, MGZ) is better than the water flow reduction effect . Rainfall characteristics, vegetation and level ditches have significant impacts on soil erosion in the Pinus massoniana forest; rainfall is the most important influencing factor for the occurrence of forest floor runoff and soil erosion; the combination of horizontal ditches and restoration of forest floor vegetation is the most effective management measure for controlling soil erosion in the Pinus massoniana forest in this experiment.