When applying the vibroflotation compaction method to treat the large-area hydraulic filled sand foundation,two key technical problems are encountered:1)How to control the clay content of the reclamation material until less than 15%；2)It is difficult to achieve the target depth once during deep underwater vibroflotation.So,combining with two overseas projects,we carry out a research on corresponding technical countermeasures.The test results show that the proposed technical countermeasures can better solve the key technical problems.