Abstract: Train ATCCB (on-board signaling system total circuit breaker) tripping off will cause ATCIS (on-board signaling system isolation switch) knob to be invalid. That relays including DCSR (data communication relay) are not electrified will cause the train emergency braking to not alleviate and doors to remain shut, seriously affecting train operation. Through Suzhou Rail Transit Line 3 train ATCCB disconnection test, the cause of this problem is analyzed, and corresponding reconstruction scheme is put forward. After the implementation of the transformation program, with ATCCB tripping off at either end of the two vehicle front ends, emergency brake alleviation can be achieved through isolating the driver end ATCIS, and the doors can be opened. The transformation scheme can be used for the existing train transformation, but also for the circuit construction of subsequently purchased additional train.