This paper introduces a low-speed outer-rotor hybrid excitation permanent magnet motor that utilizes both ferrite and NdFeB as magnetic sources. Firstly, the magnetic circuit of the motor was analyzed to clarify the path characteristics of the series and parallel magnetic circuits of the two types of permanent magnets. Then, the influence of parameters such as pole arc coefficient, permanent magnet coefficient, and permanent magnet thickness on the motor's performance is investigated. Multi-objective optimization design is conducted, taking torque, efficiency, and torque ripple as the key design metrics. Finally, the irreversible demagnetization of the motor under different permanent magnet coefficients is analyzed. The analysis reveals that a higher permanent magnet coefficient, achieved by using more NdFeB permanent magnets, contributes to providing a stable working point for the ferrite and helps prevent irreversible demagnetization.