[Objective] The effects of Polyacrylamide (PAM) applicated in separation and sediment yield process of sandy soil developed from granite parent material were determined, and the concentration threshold of PAM to increase erosion resistance of sandy soil was clarified to provide a basis for the control of Benggang erosion.[Method] Sandy soil developed from granite parent materials in Benggang erosion areas was selected. Five levels of PAM application concentrations (0 %, 1 %, 3 %, 5 %, 7 %) were set. Through runoff scouring simulation experiments, the response patterns of sediment yield rate, detachment rate, and rill erodibility of sandy soils to PAM concentration under different hydraulic conditions were studied.[Results] ① PAM significantly reduced sediment yield, detachment rate, and rill erodibility, but dramatically increased critical shear strength (p<0.01). Additionally, the sediment yield reduction effect of PAM showed a decreasing and stabilizing trend with increasing scouring time, but gradually increased with increasing application concentration, with the most pronounced average sediment reduction effect observed when PAM concentration was within 5 %. ② There was a highly significant negative correlation between soil detachment rate and PAM application concentration (p<0.001). However, as PAM application concentration increased, the rate of decrease in soil detachment rate gradually slowed down, and the effect of PAM (F=37.39, p<0.001) on soil detachment and sediment yield processes was greater than the shear strength of runoff (F=15.38, p<0.001). ③ The ratio of rill erodibility between the PAM-treated groups and the control showed a quadratic function relationship with PAM concentration (R²=0.996, p<0.001), and the efficiency of reducing rill erodibility was most significant at 5 % PAM.[Conclusion] The application of PAM effectively reduced the sediment yield rate, detachment rate, and rill erodibility of granite-derived sandy soil and increased its critical shear force. The improvement effect of PAM application showed a continuous increasing trend when the PAM application concentration was below 5 %. However, when the PAM application concentration exceeded 5 %, the improvement effect showed only a slight change. Therefore, 5 % should be considered as the concentration threshold for PAM to improve the erosion resistance of granite-derived sandy soil.