The utility model discloses a redundant structure of a loop in a power plant control system. The structure comprises a master control module installed on a mainboard, a main loop control card connected with the master control module and a terminal board A which is connected with the main loop control card and sends a signal to corresponding equipment. One side of the main loop control card is connected in parallel with a vice loop control card and a terminal board B. One end of the vice loop control card is connected with the master control module and the other end is connected with the terminal board B. The other end of the terminal board B is connected with the equipment through the terminal board A. According to the utility model, through setting the vice loop control card, a problem of shutdown maintenance when there is a fault in the main loop control card is solved so that reliability and security of the whole control system are increased. A DMA module and a delayer are used to control a line jump between the main loop control card and the vice loop control card so that a problem of cost increase caused by modification of BIOS on the mainboard is avoided. The structure of the utility model is simple. Reconstruction cost is low and a suitable scope is wide.