An auxiliary switch, for fitting and connecting to a circuit breaker, wherein the auxiliary switch has a housing, in which are provided the following: an operating handle, connected to a handle of the circuit breaker; a trip assembly, connected to a trip arm of the circuit breaker; a connecting rod assembly, which can be driven by the operating handle; a first locking rod, having a first drive part and a second drive part, wherein the connecting rod assembly can drive the first locking rod, to enable the first drive part to engage with or disengage from the trip assembly; a resettable first rotating plate, connected to the second drive part and capable of being driven by the first locking rod, wherein a first moving contact located on one side of the housing is disposed on the first rotating plate, and rotation of the first rotating plate can bring the first moving contact into contact with either one of two static contacts located on one side of the housing, to accomplish switching between a first electrical circuit and a second electrical circuit; a resettable second rotating plate, disposed concentrically with the first rotating plate and capable of being driven by the first rotating plate, wherein a second moving contact located on another side of the housing is disposed on the second rotating plate, and rotation of the second rotating plate can bring the second moving contact into contact with either one of two static contacts located on the other side of the housing, to accomplish switching between a third electrical circuit and a fourth electrical circuit; and a second locking rod, resettably connected to the housing and capable of locking the second rotating plate, wherein the second locking rod can release the locking of the second rotating plate under the action of a driving force of the first locking rod. an operating handle, connected to a handle of the circuit breaker; a trip assembly, connected to a trip arm of the circuit breaker; a connecting rod assembly, which can be driven by the operating handle; a first locking rod, having a first drive part and a second drive part, wherein the connecting rod assembly can drive the first locking rod, to enable the first drive part to engage with or disengage from the trip assembly; a resettable first rotating plate, connected to the second drive part and capable of being driven by the first locking rod, wherein a first moving contact located on one side of the housing is disposed on the first rotating plate, and rotation of the first rotating plate can bring the first moving contact into contact with either one of two static contacts located on one side of the housing, to accomplish switching between a first electrical circuit and a second electrical circuit; a resettable second rotating plate, disposed concentrically with the first rotating plate and capable of being driven by the first rotating plate, wherein a second moving contact located on another side of the housing is disposed on the second rotating plate, and rotation of the second rotating plate can bring the second moving contact into contact with either one of two static contacts located on the other side of the housing, to accomplish switching between a third electrical circuit and a fourth electrical circuit; and a second locking rod, resettably connected to the housing and capable of locking the second rotating plate, wherein the second locking rod can release the locking of the second rotating plate under the action of a driving force of the first locking rod.