The single phase line start permane nt magnet motor has high efficiency and power factor when it operates synchronous speed. The rotor structure is composed of permanent magnet and cage bars. The motor is accelerated by rotor bars and synchronized by magnet and rotor saliency. but starting torque is disturbed by magnet braking torque so, to obtain good starting performance and synchronizing capability, the design of proper permanent magnet is required. This paper is represented performance of start ing and synchronizing by changing permanent magnet thickness