Abstract: Polyacrylamide(PAM), a kind of macromolecule compound, is a new type of effective soil structure-improved additive. For the aim of applying PAM in loess region to prevent the soil and water loss and promote the effective use of precipitation, the stimulated rain experiment in laboratory was designed to study the effect of PAM on the process of runoff and sediment development. The correlative relationships between the runoff rate and the accumulative amounts of the runoff and sediment dependent on the period of rain are built. Additionally, comparing with the effect of PAM different using amounts and PAM used in different soils, the PAM 0.8 g/m² put in the surface of soil shows remarkable result in the condition of 30 min rainstorm, which reduced 87.87% sediment compared with one without PAM. The effect of PAM on Lou soil is much better than on Huang Mian soil.