The invention relates to a circuit breaker and a control device thereof. The circuit breaker comprises a motor transmission mechanism, wherein the motor transmission mechanism is used for switching on/off a switch contact; the motor transmission mechanism comprises a worm, a first dual bevel gear, a second dual gear, a third dual gear and an incomplete gear; the first dual bevel gear is meshed with a gear arranged on a motor driving shaft; the first dual bevel gear is meshed with the second dual gear; the second dual gear is meshed with the third dual gear; the third dual gear is meshed with the incomplete gear; and the worm is fixed to the incomplete gear. Through adoption of the circuit breaker and the control device thereof, the switch-on/off reliability and stability of the circuit breaker can be considered.