The objective of this study is to determine how PAM applications to a fraction of the surface affect hydraulic parameters of flow, soil water infiltration and soil sediment yield during rainfall on steep sloping land. Five PAM application rates (PAMR) 0, 0.4, 0.7, 1.0 and 1.3 g kg-1 were used for 5 sloping plots in this study. As PAMR increased from 0 to 1.3 g kg-1 at the rainfall intensity (RI) of 1.58 mm min-1, the Froude numbers decreased from 34.7 to 9.1, the Reynolds numbers (Re) decreased from 568 to 305, and the Darcy–Weisbach coefficients increased from 0.0028 to 0.041. The total runoff values were 33.8, 35.9, 31.6, 25.6 and 18.1 mm when the PAMR were 0, 0.4, 0.7, 1.0 and 1.3 g kg-1, respectively. The cumulative sediment increased rapidly with the rainfall time. In conclusion, PAM applications to a fraction of soil surface can be effective at reducing the erosion of steep sloping land.