The utility model discloses a circuit breaker, which comprises a piston rod, wherein a guide cone is arranged inside the piston rod, the guide cone is fixed inside the piston rod through an elastic fixed pin, and the position inside the piston rod which is close to the guide cone is provided with a vent hole. During the disconnecting process of the sulfur hexafluoride circuit breaker, hot airflow is jetted downwards through the piston rod, the direction of the hot airflow is changed by the guide cone inside the piston rod, the hot airflow is not returned back along the original path, but also is free from being directly jetted onto a circuit breaker cylinder or a bushing, so the performance of the product is improved, and the reliability of the product is improved simultaneously.