The invention relates to a disconnecting circuit breaker, a disconnecting switch and an electric disconnecting underframe for the disconnecting switch. The disconnecting circuit breaker comprises a circuit breaker body and the disconnecting switch. The disconnecting switch comprises a support disposed on the circuit breaker body, and the disconnecting rotating shaft is rotatingly installed on thesupport. The support is provided with a motor that rotates in a forwarding manner to drive the disconnecting rotating shaft to carry out the switching-on rotation. The disconnecting circuit breaker also comprises a travel switch structure which is triggered at the tail end of the switching-on rotation of the disconnecting rotating shaft to control the stopping of the forwarding rotation of the motor, and is triggered at the tail end of the switching-off rotation of the disconnecting rotating shaft to control the stopping of the reverse rotation of the motor. The disconnecting circuit breaker also includes a triggering portion for triggering the travel switch structure, wherein one of the triggering portion and the travel switch structure is disposed on the support, the other is disposed onthe disconnecting rotating shaft. The motor is employed for driving the disconnecting rotating shaft to rotate, and reduces the labor intensity of an operator. The cooperation of the travel switch structure with the triggering portion can improve the motor drive reliability.