Disclosed is a circuit breaker chassis comprising a moving chassis (22) and a screw rod (211), and further comprising a cross beam (21), a locking and driving device (20) having a twin dead centre mechanism and a rotary auxiliary switch (29), wherein the cross beam (21) is detachably fixed in a switch cabinet; the screw rod (211) is mounted on the cross beam (21); the screw rod (211) rotatably moves, thereby driving the moving chassis (22) to move away from and near the cross beam (21); the rotary auxiliary switch (29) comprises an auxiliary opening and driving piece (291) capable of rotatingaround a rotary centre (292), and two pairs of auxiliary opening contact sets encircling the rotary centre (292); the locking and driving device (20) having a twin dead centre mechanism comprises a guide groove piece (204) rotating around a guide groove piece rotary centre (205); and one end of the guide groove piece (204) is provided with a guide groove (2041), and the other end is connected to an elastic soft connecting member, one end of the elastic soft connecting member being fixed.