The invention relates to an auxiliary disengaging mechanism for a breaker, comprising an electromagnetic relay, a four-bar mechanism, a lock catch, an energy storage spring, a revolution spring for resetting a handle and an interlocking mechanism for lock/unlocking. The interlocking mechanism is formed by a cylindrical surface on the lock catch and a plane on a transmission rod in the form of extruding contact; the lock catch is positioned in a three-point restraining manner by the interlocking mechanism, a hinge shaft hole and a backstop structure, and the restraining force is supplied by an element mounted on a drive rod. Therefore, the invention not only enhances the stability and the reliability of the auxiliary disengaging mechanism, but also remarkably reduces the machining and assembling precision, the manufacturing difficulty and the production cost.