AC induction machines are widely used in electric servo drive, information processing, transportation and other fields. However, the unexpected faults cause the serious threat for the normal operation and operator’s safety. Therefore, timely faults diagnosis is an effective way to ensure the AC induction machines to work in health condition. In AC induction machines, magnetic field is the basis of energy conversion of motor, and the faults have the directly influence on the electromagnetic field distribution. In this paper, 2D numerical model of the AC squirrel-cage asynchronous induction machine is built by using COMSOL Multiphysics according to finite element method; Then, the magnetic flux distribution of AC induction motor with three different faults which commonly occurs in engineering are simulated. Base on the numerical simulation, the influence of the different faults on the magnetic distribution is discussed in detail. The investigation is beneficial to find a nondestructive fault diagnosis approach to the induction machine.