Abstract: The application of vacuum dynamic consolidation method to improve a large hydraulic fill ground in Shanghai was presented.The variations of ground water table and excessive pore water pressure during and after the execution of the improvement were monitored.Based on the field observations,the underlying mechanism of vacuum dynamic consolidation was proposed and the criteria for determining two crucial parameters of the improvement were discussed.This study verified the feasibility of the vacuum dynamic consolidation method to improve large area grounds with hydraulic fills,such as those at wharves or harbors in coastal areas or highway constructions.