Permanent magnet generator is kind of electrical machine widely used in our daily life nowadays. This paper, dealt with the optimal design to reduce the cogging torque reduction of permanent magnet generator. For the purposed of study, the integral slot number of 48 slots/6 poles with radial magnetization have been selected. The magnetic flux distribution at the air gap and core of any electrical machine was analyzed and presented in the paper. The cogging and ripple torque is the most issues in permanent magnet generator design. The cogging torque is influenced by the magnetic flux distribution in air gap. To reduce cogging torque, is one of difficult task, since it is influenced by many factors in both the stage of design and stage of manufacturing. In the stage of design, the cogging torque has been exist caused by effect of material used in the machine structure. This paper dealt with cogging torque reduction at the stage of design by applying notching in the magnet edge of the permanent magnet generator. The finite element analysis has been used to compute the permanent magnet generator performance. Using the finite element of FEMM, it was found that the cogging and torque ripple could be reduced effectively compared with the initial structure. They could be reduced as much as 98.8 % compared with the initial structure.