To ensure the strength of the hull structure of polyethylene fishing boats and improve the quality of polyethylene fishing boats, a 10.10 m long linear low-density polyethylene fishing boat was taken as the research object, and the finite element model of fishing boats was established by using ANSYS software. According to the relevant requirements of the current technical regulations, the impact of the total longitudinal strength on the safety of fishing boat structures under the combined bending and torsion loads under typical working conditions was analyzed. Through the method of adjusting the length depth ratio of the ship and ensuring the continuity of the structure at the main hull fish compartment, The influence of the ratio of the ship's principal dimensions and the continuity of hull structural members on the longitudinal strength of the main hull is studied. It can be seen from the research that the quality of raw materials of polyethylene fishing boats is the primary factor to ensure the safety of the hull structure. It is necessary for small polyethylene ships to check the overall longitudinal strength of the whole ship. Proper main dimensions of the ship can significantly improve the overall longitudinal strength of fishing boats. Ensuring the integrity and continuity of the longitudinal structure during ship design and construction is more conducive to the transition of the overall longitudinal bending stress. The direct calculation method adopted in this study can provide a reference for the research on the structural strength of polyethylene fishing vessels and the structural optimization design of polyethylene fishing vessels.