The demagnetization characteristics of the permanent magnet synchronous machine (PMSM) are investigated using the finite elements method. This is done to resolve the partial demagnetisation of the PMSM rotor, resulting from the short-circuited magnetic field of the first turn of the phase belt (FTPB). This paper first introduces the electrical machine design parameters and winding construction, after which it establishes the PMSM model using Ansoft Maxwell software. The harmonic contents of the waveform are studied by investigating the magnetic flux density distributions before and after the short circuit fault, the varied trajectories of the flux densities of the reference points on the rotor permanent magnet (PM) located in different points, the no-load air-gap magnetic flux density, the electromagnetic torque of the PMSM, the three-phase currents, and the harmonic content of waveform. In addition, the reason why the FTPB is short-circuit is determined, which can provide a theoretical basis for the diagnosis of the PMSM.