The invention relates to a control circuit and a control method for a safety power supply of a signal system. The control circuit comprises a first downtime control circuit, a second downtime controlcircuit and an execution unit; the signal system comprises two host modules; the first host module and the second host module are respectively connected with the execution unit through the first downtime control circuit and the second downtime control circuit, the input end of the execution unit is connected with a vehicle-mounted power supply, and the output end of the execution unit is connectedwith the first host module and the second host module through a power conversion circuit. When the system is shut down, the power for the two main hosts is disconnected at the same time to ensure that the power is completely disconnected and there is no safety risk; the hosts detect the status of the execution unit at the same time; when the host of the main system detects that the execution unitis abnormal, the system can be oriented to the safety side; when the system enters the down state, the system is kept in the down state, and can exit the down state by re-powering through a manual mechanical switch K4, so that the safety of the system is ensured.