Abstract： Taking the deep water foundation of Qiongzhou Strait Bridge as the research object, and aimed at the issue of dynamic stability of deep water foundation of extra large bridge, the disastrous factors such as seismic load, ship impact load and wave forces were considered. Based on the dynamic FEM, the characteristics of dynamic response of the deep water foundation, the displacement response under the actions of multiple disasters were explored and analyzed. The caisson of the foundation represents without any phase difference basically under seismic force, and maximum displacement reaches 24.4 cm. The horizontal displacement reaches 15.1 cm under ship impact force, and 10.8 cm under wave force. The pile group shows complex response under dynamic load. Due to the constraints of soil and function of inertial force of the caisson, the relative displacement between the pile body and caisson is large, which leads to obvious stress concentration at pile head. The results can provide references for the design and construction of deep water foundation, especially for Qiongzhou Strait Bridge.