Because there exist eddy current loss in permanent magnet, it will give off in the form of heat. This will cause high temperature in disc permanent magnet synchronous motor (DPMSM). When the temperature is too high, it will cause the problem of degenerate performance of the motor. So conducted intensive studies on the permanent magnets of motor, and further research on these issues was of great significance to improve the performance of disc permanent magnet synchronous motor and its optimization design. In order to reduce the eddy current loss of permanent magnet, the methods of the permanent magnet segment and shielding layer was used. Maxwell, threedimensional finite element analysis software, was used to establish the finite element model of the motor, reveal the electromagnetic distribution around permanent magnet and receive the average eddy current loss of permanent magnet when the motor was driven by threephase sinusoidal current source. The method, segment in several different directions and simulation, was applied to show that the splitting into three pieces horizontally was the best by comparison, when the permanent magnets were segmented. Firstly, the principle’s reliability should be verified, and then the optimal value of shielding layer thickness could be get by MATLAB curve fitting, when using the electromagnetic shielding principle reduce eddy current loss.