Surface crust of soil, especially Loess, formed under the impact of raindrops will significantly affect rain water infiltration rate. Polyacrylamide(PAM) can effect ively prevent crust formation and improve soil structure and enhance soil permeability. To clearly relate PAM application with infiltration rate, experiments were conducted with rainfall simulator under laboratory conditions, at 3 different levels of rainfall intensity: 50 mm h^-1, 100 mm h^-1 and 150 mm h^-1;4 slope gradients: 8.74%, 17.63%, 36.4% and 46.63% and 5 surface treatments: control, straw coverage and three PAM coverages-A, B, and C. Two rainstorms were simulated with a 24 h interval. Analyses were made to relate infiltration rates with PAM coverage and describe impacts of PAM application on infiltration.