[Objective] In response to the high requirements including torque density, operating efficiency, and reliability for large transmission components used in aviation, as well as the mechanical gears have problems including easy wear, lack of overload protection, and high maintenance costs. Therefore, a large magnetic field modulation gear is designed in this paper. [Methods] Through analysis for the structural characteristics and design requirements of large magnetic field modulation gears which used in aviation, torque transmission density would be increased as much as possible while considering performance such as efficiency and torque fluctuation. A nonlinear constrained genetic algorithm was used for multi-objective optimization design. Based on the optimized electromagnetic design scheme, finite element method was used to analyze the electromagnetic characteristics, stress distribution characteristics for key components, and temperature rise during operation. [Results] According to the results of multi-physics field analysis, the output power of the proposed magnetic field modulation gear had been reached 500 kW. It could operate smoothly with an efficiency reached 96.17%. The laminated magnetic adjustment block and permanent magnet laminations could effectively reduce core-loss. During its stable operation, the stress of key components inside the rotor could meet the strength requirements by using carbon fiber as the rotor binding sheath, and the temperature of each component had not exceed the allowable material temperature. [Conclusion] The analysis results have verified the rationality and feasibility for the design, which providing a theoretical basis for the design and application of large aviation magnetic field modulation gears, and having certain engineering reference value.