Soil formation is the basis for determinantion of soil permissible erosion rate. In this study, soil formation rates (SR) of the purple soils (Regosols) different in parent material, vegetation and thickness in hilly areas of Sichuan, China were calculated using the Barth model that is based on the material recycling theory, and measured at the stationary experiment sites in the field. Results show that estimated-SRs were generally, smaller than measured-SRs, and varied significantly with parent material, but not with vegetation or soil depth. Moreover, they were closely related to runoff volume. Measured-SRs varied substantially between the treatments, owing to different characteristics of soil parent materials and different temperature and soil moisture at the interface between soil and parent materials. In terms of measured-SR the three types of soils showed an order of J₂s> J₃p> J₃s, and the three vegetations did an order of crop> trees> grass. The general trend of soil formation rate in relation to soil depth was that the thinner the soil layer was; the higher the rate was. Based on the measured-SR, the SR was determined to be 800 t km^-2 a^-1 for J₃s purple soils, and 1 200 t km^-2 a^-1 for J₂s purple soils and for J₃p purple soils in the study region.