This paper studies the effects of increasing the number of rotor poles on the air gap flux density waveforms in permanent magnet (PM) motors. The aim is to reveal the harmonic behavior of the working flux in the air gap, which controls the performance, and the operational behavior of the whole machine. For the comparison purpose, the rotor is designed to have 4 and 8 poles mounted on the same rotor iron surface and the excitation currents were rearranged so as to produce 4 and 8 poles respectively without changing the stator structure. FEM analysis is performed with ANSYS software and adopted to obtain the working flux waveforms, and MATLAB is used to extract harmonic spectrum of the flux waveforms. The result demonstrates that there are more harmonic components contained in the working flux as the number of slots per pole per phase decreases.