The dynamic behavior of open-ended pipe driven by a hydraulic hammer will be studied in this project, and the mechanism of underwater acoustic radiation of the pile will be investigated. The influencing factors of underwater noise and its reduction way will be researched. Modeling the impact on the pile head and the soil around the pile toe, a nonlinear non-stationary dynamic model of the pile in driving will be obtained. A semi-analytical method will be used to calculate underwater sound. By using constrained variation principle and mode expansion method, the elastic wave excited by the impact will be obtained in series form. And then the underwater sound radiation can be calculated according to the vibration solution. The influencing factors of the underwater sound will be investigated, and the sound reduction approaches will be explored.