Leakage permeance of a permanent magnet (PM) is an important factor for improving the accuracy of electromagnetic device calculations based on a magnetic equivalent circuit (MEC). For PM leakage permeance calculations, the traditional simulation method of finite element analysis (FEA) and the lumped parameter analytical method (LPAM) have been considered; it was found that FEA has the disadvantage of a long calculation time and LPAM has low accuracy. The magnetic field lines distribution analytical method (MFLD) is proposed in this paper in order to raise computational efficiency and keep accuracy within a certain range. The electromagnetic features of open circuit fan-shaped PMs are presented by MFLD and finite element analysis (FEA) is adopted to match the MFLD results. In order to verify the validity of the proposed method in a magnetic system, the working points of PMs in an electromagnetic actuator are calculated, and the numerical results compared with the experimental results.