Abstract: This paper presents the insitu tests for improving saturated soft soil ground formed by hydraulic fill method. The wellpoint dewatering method and roller compaction method are used firstly in order to obtain initial bearing capacity. After this,the bearing capacity can be advanced obviously by dynamic compaction method. This new method is named as dynamic compaction method with predewatering in this paper. According to a large number of insitu test results,this paper studies the problems such as the affecting scopes of wellpoint dewatering,pore water pressure induced by dynamic compaction,deep settlements of soil layers. In the meantime,number of passes,number of drops per pass,duration time between various passes,and other factors are also discussed. The studies show that the bearing capacity of soft soil ground can be greatly increased using dynamic consolidation with predewatering method. 