The invention provides a novel circuit breaker. According to the circuit breaker, inherent problems such as arcing of contacts of traditional mechanical switches, ageing of contact springs and the like can be effectively solved, switching speeds are greatly increased, service lives of the switches are prolonged, and the extreme requirements of sensitive and critical loads for the power supply reliability and the electric energy quality are met. The circuit breaker comprises a circuit breaker body, a protection unit, a data acquisition unit and a controller, wherein the circuit breaker body is arranged between a line incoming end of a main power supply line and a user; the protection unit is connected with the circuit breaker body in parallel; the data acquisition unit is connected with the circuit breaker body and acquires electric signals of the main power supply line through a sensing device; and the data acquisition unit and the protection unit are connected with the controller respectively. According to the circuit breaker, 'power switching' is actually formed when the circuit breaker is turned off, the switching time reaches the millisecond level, seamless switching can be realized, the rapidity and the transient characteristic are ideal, and the extreme requirements of the sensitive and critical loads for the power supply reliability and the electric energy quality are truly met.