The utility model discloses a bus type road signal system and the a working method thereof. The bus type road signal system comprises a signal machine, a standard AC power supply cable and N signal lamps, wherein the N is a natural number. The signal machine is provided with an A interface and a B interface; the standard AC power supply cable returns to the B interface by starting from the A interface and going through all N signal lamps; the B interface and the A interface are conducting by power and the communication signals are isolated to form an annular link; and the annular link receives the external power supply through the signal machine. The bus type road signal chooses the unique wire arrangement mode, and all components on the annular link are working by receiving power from the link. The annular connection guarantees that each node is supplied by the double-line redundant power, so that when any of the nodes occurs the line disconnection fault, the power supply system can still normally operate. When multiple nodes occur line disconnection fault, part of the devices can be guaranteed to operate. In the meantime, based on the power supply link and the unique communication mechanism and mode, the bus type road signal system guarantees the communication double-line redundant of each node, improves the reliability of the system and keeps working when the physic links occurs abnormal condition.