A trip structure of a circuit breaker comprises an operating mechanism and an electromagnetic tripper, wherein the operating mechanism is in linkage with an operating handle of the circuit breaker to drive a movable contact assembly to swing and match with a static contact, the operating mechanism comprises a jump pin and a lock which are buckled and connected, an extension end is arranged on the lock and is matched with a top rod of the electromagnetic tripper, and a trigger bulge is also arranged between the lock and the movable contact assembly; and when the circuit breaker is circuit-shorted, the top rod of the electromagnetic tripper collides with the extension end of the lock, the movable contact assembly swings to push the lock via the trigger bulge by means of an electric repulsive force between a movable contact of the movable contact assembly and the static contact, and the lock and the jump pin are pushed to be unlocked jointly by the top rod of the electromagnetic tripper and the movable contact assembly. In the trip structure of the circuit breaker, provided by the invention, the circuit breaker is rapidly tripped by additionally arranging the trigger bulge between the lock and the movable contact assembly, the trip structure is simple and reliable, a fusion welding phenomenon occurred between the movable contact and the static contact caused by long trip time can be effectively prevented, and the disconnection capability of the circuit breaker is improved.