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.