A circuit breaker and a power distribution system are provided. The circuit breaker includes a housing and an internal element disposed inside the housing. The housing includes a front panel and a rear panel that are disposed opposite to each other, the front panel is disposed with a button, a status display unit, and a power wiring port, and the rear panel is disposed with a power interface and a signal interface. The power wiring port and the power interface are connected to a circuit of a power distribution system. The signal interface is internally and electrically connected to the button, the status display unit, and the internal element, and the signal interface is externally configured to be electrically connected to a control unit disposed outside the housing. A control signal of the control unit implements working of the button, the status display unit, and the internal element.