The invention relates to an auxiliary 
tripping unit of a 
circuit breaker and belongs to the technical field of miniature circuit breakers. The auxiliary 
tripping unit and an operating mechanism part of the 
circuit breaker are connected and mutually driven to play a role in auxiliary 
tripping and self-resetting, a 
magnetic flux converter and an auxiliary tripping mechanism are arranged on a modulebase, the auxiliary tripping mechanism comprises a reset lever, a module tripping rod and a module lock catch, the 
magnetic flux converter assists completion of tripping action through the action of the movable ejector rod and the auxiliary tripping mechanism, and meanwhile, the tripping mechanism is assisted to complete the reset action. Through the technical scheme of a secondary lock catch, theoutput of the release type 
electromagnet is amplified, the tripping force is increased, and the 
magnetic flux tripper can be reliably tripped under the condition of limited energy input, the magneticflux tripper is reset while tripping is carried out, so tripping and resetting functions are realized, manual reset is not needed, and the risk that the 
reset button is stuck is reduced, the output requirement of the 
electronic circuit board on the release is reduced, and reliability of the product tripping action is improved.