The accurate analysis of motor modal is an important part to realize the low noise drive design of motor. When the modal frequency of motor is close to the frequency of corresponding order radial electromagnetic force waveresonance will occur. Taking a 6-pole 36-slot 70 kW commercial vehicle owner driven permanent magnet synchronous motor as the research objectthe influence of the rotor with auxiliary slot and the rotor with segmental skewed pole method for the first-order tooth harmonic on the electromagnetic force wave is compared and analyzed. The amplitude of the 0-order 12-time frequency radial electromagnetic force wave can be reduced by 79% after adopting the optimized method of rotor with auxiliary slot and rotor with segmental skewed pole. The three-dimensional finite element modal simulation model of the motor is established. The influence of the motor structural components on the modal is analyzed. Combined with the installation and fixation methods of the common vehicle mounted drive motorthe shell is constrainedand the modal characteristics of the motor under different constraints are analyzed. The results show that under the working condition of peak power of 8 000 r/minthe amplitude of radial electromagnetic force with 0-order 12-time frequency under the optimized design scheme is largebut the frequency is 4 800 Hzfar away from the natural frequency of the motor modalso resonance will not occur and the electromagnetic noise is reduced.