The red soil hilly region,located in the tropical and subtropical zones of Southeast China,spreads over 9 provinces and 1 autonomous region.With plentiful light,heat and water resources,it enjoys high potential for agricultural and economic development.However,soil erosion and seasonal drought are major restraints for sustainable agriculture as a result of improper land use and uneven distribution of rainfall.Soil aggregate stability has substantial effects on soil porosity and,therefore,may influence infiltration rate and runoff processes of rainfall.The objects of this study are to determine relationship between wetting rate and runoff and soil loss.Red soils derived from Quaternary red clay were collected and packed in 0.6 m×0.3m trays,separately,wetted at 3 wetting rates(2,10 and 60 mm h^-1),and then exposed to simulated rainfall with an intensityof 60 mm h^-1 in laboratory.The Le Bissonnais’method was applied to simulating the breakdown mechanisms of slaking in fastwetting,stirred wetting,and slow wetting.The aggregate stability index,i.e.mean mass diameter(MMD),indicated that fast wetting caused the most severe disruption of aggregates.The MMD in each soil ranked in the order of slow wetting,stirred wetting,fast wetting.Significant correlation was observed between soil loss,runoff rate and wetting rate.The results show that the runoff rate increased with wetting rate,ranging from 0.58 to 0.96 mm min^-1.In each soil exposed to slow wetting rate,less soil loss was noted.Wetting rate also played a great role in determining sediment materials.The largest MMD of sediment materialswas found in soils exposed to fast wetting.