The method of vacuum dewatering united with dynamic compaction is widely used in the treatment of dredger fill subgrade.Based on the previous research and the engineering of soft soil foundation treatment on the harbor of Weifang,we study the effect of vacuum dewatering depth and soil permeability on dynamic compaction.The results show that with a reasonable layout of the tube wells of different depths,the effect is small even if the soil permeability changes greatly,and this united method works best when the dewatering depth is about 3 m.