The invention provides an operating mechanism of a breaker. The operating mechanism of the breaker comprises a frame assembly, a switch-on control assembly, an auxiliary lever and a switch-on readiness indication assembly. A switch-on slide bar is provided with an abutting and pressing drive portion and an indication matching surface. A cam device comprises a disk. A first extension arm, a second extension arm and elastic sheets are arranged on a switch-on rotating member, wherein the first extension arm is matched with a sunken portion on the outer edge of the disk, and the second extension arm is matched with the abutting and pressing drive portion of the switch-on slide bar. The auxiliary lever is arranged on a side board in a pivoted mode and is hinged to a moving contact of the breaker through swing connecting rods, and the side portions of the auxiliary lever are provided with cam shafts matched with the elastic sheets. The cam shafts are located between the disk and the elastic sheets. The switch-on readiness indication assembly comprises a switch-on readiness indication part and a second spring. The operating mechanism of the breaker can clearly indicate for operators that the operating mechanism is in a state that energy storage is completed and the operating mechanism will be switched on; meanwhile, the operating mechanism is compact in overall structure and high in transmission reliability.