In response to the challenging environmental conditions of large waves and strong currents faced by dock structures under deep-sea conditions,combining the advantages of conventional mature pile foundation and gravity-type dock structures,the use of a new composite structure combining a gravity-type caisson and pile foundation can effectively save construction time and reduce project costs.The cross section design and parameters of the composite structure are determined and optimized by comparing with the traditional structure of the trial project.With reference to the calculation model of gravity-type structures,considering random variables such as material properties,geometric parameters,and design loads of the composite structure,the reliability index of new composite structure against sliding and tilting is calculated using the JC method,and the results show that the composite structure is reasonable.