The invention provides an electric operating mechanism of a circuit breaker. The electric operating mechanism comprises a housing, a transmission shaft, a driving device, a striking device, a position detection device and an electric control device, wherein the position detection device comprises a switch-on position detection device, a switch-off position detection device and a free position detection device; the switch-on position detection device and the switch-off position detection device are arranged on the two sides around the transmission shaft; and the free position detection device is arranged at the driving device far away from the transmission shaft. Distribution of the position detection devices is relatively disperse; the position detection devices are free from false detection when a first detection object and a second detection object are respectively detected; and a detection range is large due to the arrangement manner of the position detection devices.