The drive motor is the core component of electric vehicles, its comprehensive performance requirements are extremely high, AC induction motor due to the cast aluminum rotor is often used, making the rotor broken bars and thin bars defective faults are very common, based on the driving safety, comfort, and other considerations, it is very necessary to explore these faults on the performance of the motor impact law. In summary, the article mainly analyzes the magnetic field and NVH changes of the rotor defective faults of a certain AC induction motor for electric vehicle drive, and the specific work is as follows: firstly, according to the cast aluminum rotor structure adopted in a certain drive motor, the finite element model of different defective faults of the rotor is established by using the equivalent resistance method; secondly, the influence law of different degrees of defects of the rotor guide strip on the electromagnetic field of the motor is compared, and the preliminary determination of the faults make the It is initially determined that the defects cause obvious distortion of the local field quantity of the motor, which in turn causes a sharp increase in the rotor guide current, electric density and torque fluctuation. Finally, theoretical analysis and simulation calculations are carried out for the impact of NVH, and the results show that the failure of the guide strip will additionally generate low-frequency electromagnetic force smaller than the fundamental frequency of the electromagnetic force, and the number of broken strips increases dramatically, which will bring about a serious NVH problem.