A sludge concentration area will come into shape as a result of using the sand source with high soil content in large area of reclamation operation. In this regard it is an engineering task to be solved to conduct foundation reinforcement of ultra-thick silt stratification, especially exploration of the bearing stratum of earth’s surface. This article provides a reference for similar projects as the foundation reinforcement of extra-thick silt stratification, especially on the formation of the bearing stratum of earth’s surface through learning the key technologies of exploration of the bearing stratum of earth’s surface of the Yangshan deepwater port west III ultrathick sludge area.