A protective circuit for a motor includes a motor, a drive unit and a control unit. The drive unit is connected to the motor to drive the motor. The control unit is connected to the drive unit to control output or drive current of the drive unit. The motor and the drive unit are incapable of generating high temperature due to excessive drive current being limited by the control unit such that damage of the drive unit and the motor can be avoided. The control unit is a comparator or an operation amplifier connecting with a comparison circuit composed of a capacitor and a plurality of resistors to produce control signal.