In view of the problems such as the blockage of drag head and weak ability of breaking soil when excavating hard clay，we compare the properties of hard clay and soil in the Yangtze River and find that the hard clay has the characteristics of large cohesion，fine particles and high shear strength. Based on the numerical simulation and adopting the technology of ultra-high pressure jet to solve the above problems，we develop a set of efficient excavating hard clay drag head system with independent intellectual property rights（with the maximum pressure of 38 MPa），which adopts the mode of “high-pressure head，low flow“ to reduce the excavation resistance，alleviate the problem of rake blocking，and increase the soil breaking capacity，to provide a technical support for channel dredging projects.