Permanent magnet vernier machines (PMVMs) have been lately attracting attention due to its high torque density characteristic. This paper introduces how to estimate air gap flux density waveform of spoke array PMVM using the magnetic circuit that we propose to reduce the labor of initial model design and improve the efficiency of the whole machine design. The output torque can also be calculated from the fundamental component and the harmonic contents of the waveform. Those were compared with the results obtained from Finite Element Analysis (FEA). The fundamental component of the air gap flux density waveform and the average value of torque were in good agreement with the result from FEA. However, the harmonic contents had somewhat error.