Abstract: Objectives:Composite materials are widely used in the superstructure of ships,and the study of the ultimate strength and gradual failure process of large-scale composite structural connectors is not only of great significance for maintaining the structural and performance safety of ships, but also support for the performance optimization design of subsequent composite structures. Methods:In this paper, the study is carried out from two aspects:structural test and numerical simulation for the bolted connection structure of the steel base and the composite stiffened plate of a certain equipment on the ship. Results:The test results show that the structure reaches the limit of bearing capacity when the bending moment reaches 50.92 kN·m, and the ultimate bending moment obtained by numerical simulation is 52.86 kN·m. The main failure mode of the structure is the debonding of the adhesive layer of the cap rib and the sandwich panel, at the same time, the fiber fracture and matrix cracking of the sandwich panel occur in the bolted connection area. Conclusions: The ultimate load and failure mode obtained by numerical simulation are in good agreement with the test results, which indicates that the progressive damage analysis method can better simulate the failure process of complex connection structures.