Abstract: In order to study the impact of applied polyacrylamide (PAM) on the soil physics and the distribution of soil water content under the natural condition, an experiment and research on eleven various PAM amounts plots of Alfalfa and one bare plot have been studied. The results showed that during the 0-2 g/m2 of PAM amount, the bulk density decreased with increasing amounts of PAM but the saturated hydraulic conductivity increased. The bulk density increased and the saturated hydraulic conductivity decreased when the concentration of PAM was higher than 2 g/m2. During the range of 0-3 g/m2 the changes between the bulk density, saturated hydraulic conductivity and concentration of PAM could be modeled by quadratic equation. The surface soil moisture increased with the increasing amounts of PAM. There were no significant difference about the soil moisture between 20-60 cm and 100-200 cm depth, while the soil moisture increased in 60-100 cm with the increasing amounts of PAM in the range of 0-2 g/m2 but decreased when the concentration of PAM was higher than 2 g/m2.