The present invention relates to a protection circuit and a ground fault circuit interrupter. A protection circuit may include a power supply circuit, a ground fault detection circuit, a signal amplifying and shaping circuit, a microcontroller control circuit, a power supply detection and indicator circuit, a tripping mechanism control circuit, and a reverse grounding detection and execution circuit. The microcontroller control includes a microcontroller, a first capacitor, and a reset filter circuit. The reset filter circuit comprises a reset IC, a second capacitor, and another capacitor. A ground fault circuit interrupter may comprise an interrupter body with a protection circuit in the interrupter body. The practice of the present disclosure may address installation safety risks of conventional ground fault circuit interrupters and arc fault circuit interrupter and improve the safety of ground fault circuit interrupters.