Prediction of the self-propulsion performance of seawater MHD underwater vehicles is of great significance for the design and rapid optimization of the vehicle. Based on a typical advanced two-pole superconducting magnet (with a large warm hole of 260 mm and a high magnitude of the magnetic field of 6.5 T) which is close to practical application, this paper considers the underwater vehicle with the most promising application prospect of the MHD thruster as a research object. Based on the Fluent MHD module, using the full three-dimensional CFD numerical simulation method, and starting from the coupling mechanism of electric, magnetic and fluid physical fields of the MHD thruster, the paper analyzes the generation sources, influencing factors, and variation laws of thrust under self-propulsion from the point of view of electromagnetic, pressure and viscous forces. Efficiency characteristics of MHD thrusters are analyzed by considering propulsion, channel, electromagnetic, and jetting efficiency. Finally, a more comprehensive self-propulsion performance of the seawater MHD thruster is obtained. Key words: Seawater MHD thruster, self-propulsion performance, thrust distribution, three-dimensional numerical simulation. Tables 2, Figs 26, Refs 22.