The simulated rainfall experiments were conducted under different slopes (15°, 20° and 25°) combined with different Polyacrylamide (PAM) application rates (0, 0.4, 0.8 and 1.6 g/m²) and different rainfall intensities (60, 90 and 120 mm/h) in this research. The process of runoff and erosion for the sheet erosion of purple soil slopes under different PAM application rates, the influence degree of PAM on the erosion and runoff and their main influence factors were analyzed. Also, the interrill soil erodibility under different PAM application rates was also evaluated. The results showed that the processes of runoff rate and erosion rate increased at first and then was stable with fluctuation, and decreased rapidly at first and was stable with fluctuation, respectively. PAM did not affect the runoff and erosion process of sheet erosion. The runoff amount and erosion amount decreased by 7.71%, 35.16% and 21.12% and by 35.80%, 49.39% and 17.85% for the PAM application rate of 0.4, 0.8 and 1.6 g/m², respectively, when compared with the no PAM application condition. The runoff reduction benefits of different PAM application rates followed the sequence of 0.8 g/m² > 1.6 g/m² > 0.4 g/m² for different rainfall intensities, while the sediment reduction benefits were affected by the slope. On the 15° slope, the order of magnitude of sediment reduction benefit of PAM application was 0.8 g/m² > 1.6 g/m² > 0.4 g/m², while the order of magnitude was 0.8 g/m² > 0.4 g/m² > 1.6 g/m² on the 20° and 25° slopes. The application of PAM could effectively reduce the interrill soil erodibility. The order of magnitude of the effect was 0.8 g/m² > 0.4 g/m² > 1.6 g/m², which was reduced by 54.40%, 40.94% and 18.21%, respectively, when compared with the no PAM application condition.