A plug-in circuit breaker comprising a circuit breaker housing and at least one protective pole, said circuit breaker housing being providing with at least one protective pole-mounting cavity, wherein each protective pole includes the operating button , an operating mechanism arranged inside said protective pole-mounting cavity and drivingly connected with said operating button , a protecting mechanism drivingly cooperated with said operating mechanism , an arc extinguishing system , a first wire-inlet terminal , a first wire-outlet terminal , a movable contact connected with said operating mechanism , and a stationary contact fitting with said movable contact ; wherein one end of said operating button is inserted into the circuit breaker housing, at one end of which said operating button and said first wire-outlet terminal are both arranged, and at the other end of which said first wire-inlet terminal is arranged, said arc extinguishing system is arranged in the middle of said protective pole-mounting cavity, said operating mechanism is arranged between said operating button and said arc extinguishing system , and said protecting mechanism is arranged between said first wire-outlet terminal and said arc extinguishing system and positioned on one side of said operating mechanism ; wherein in the case that the plug-in circuit breaker is in a make-contact state, and said operating mechanism is in a locking state, while a short-circuit fault and an overload fault occurs, said protecting mechanism actuates said operating mechanism to trip off; said protecting mechanism includes a magnetic yoke and a dual metal piece , and said operating mechanism includes a jump buckle and a lock catch ; when a short-circuit fault occurs, said lock catch is attracted to swing toward said magnetic yoke , releasing the interlock with said jump buckle ; when an overload fault occurs, said dual metal piece bends and actuates said lock catch to swing toward said magnetic yoke , releasing the interlock with said jump buckle . wherein one end of said operating button is inserted into the circuit breaker housing, at one end of which said operating button and said first wire-outlet terminal are both arranged, and at the other end of which said first wire-inlet terminal is arranged, said arc extinguishing system is arranged in the middle of said protective pole-mounting cavity, said operating mechanism is arranged between said operating button and said arc extinguishing system , and said protecting mechanism is arranged between said first wire-outlet terminal and said arc extinguishing system and positioned on one side of said operating mechanism ; wherein in the case that the plug-in circuit breaker is in a make-contact state, and said operating mechanism is in a locking state, while a short-circuit fault and an overload fault occurs, said protecting mechanism actuates said operating mechanism to trip off; said protecting mechanism includes a magnetic yoke and a dual metal piece , and said operating mechanism includes a jump buckle and a lock catch ; when a short-circuit fault occurs, said lock catch is attracted to swing toward said magnetic yoke , releasing the interlock with said jump buckle ; when an overload fault occurs, said dual metal piece bends and actuates said lock catch to swing toward said magnetic yoke , releasing the interlock with said jump buckle . <EOS>