Abstract: Experimental studies on water level effect for dynamic compaction performance were presented by using the single-point impact system developed by the authors.Meanwhile,an automatic cone penetrometer was also developed to acquire the cone resistance in soil samples.It was indicated that after impaction,the measured increments of excess pore water pressure increased when the water level increased,and the cone resistance(QR) in soils with higher water level was found less than that in soils with lower water level and far less than that measured in dry soils.The terms of improvement ratio(IR) and penetration work(Wq) done were introduced to evaluate the overall performance of improvement.