The marine shaft belt permanent magnet generator, directly mounted on the ship's main shaft, uses the main engine's surplus power for power generation, enhancing fuel efficiency, reducing reliance on auxiliary generators, and cutting operating costs and pollution. Compared to traditional diesel generators, it boasts high efficiency across a wide speed range, a compact structure saving ship space, low maintenance costs, high reliability, and suitability for long-term marine operation. A study on an 840 kW, 60 r/min low-speed permanent magnet motor systematically summarizes domestic and international R&D status. Based on electromagnetic principles, key parameters (radial/axial dimensions, air gap, stator materials, winding configurations, rotor structure) were researched. Using Motor-CAD, a 2D finite element model was developed, iteratively optimizing parameters like permanent magnet thickness, air gap length and number of winding turns. Simulations analyzed electromagnetic and loss characteristics, establishing design criteria for marine shaft permanent magnet motors. Results show all performance indicators meet requirements, verifying the method's feasibility.