In order to solve the problem that the primary or both the primary and the backup multiple function processor (MFP) modules were offline simultaneously in the DCS of 300 MW units in Shaoguan Power Plant, with the analysis of the communication between the primary and backup MFP modules and the prefabricated cable, the cause of MFP module fault was found. After proving the compatibility of BRC-300 controller and MFP module, 10 pairs among the 29 pairs of MFP modules were promoted to BRC-300 controller; the configuration software in the control system was also promoted. Then, the integrity of BRC-300 controller configuration was checked. Meanwhile, the daughter board chip of network processing module was upgraded to avoid the interruption of data transmission between BRC-300 controller and other MFP modules. The good communication between BRC-300 controller and MFP modules could be realized by using control channel bus. Finally, the correctness of the design scheme was proved by the actual operation, thoroughly solving the offline problem of redundant MFP modules, as well as ensuring the safe operation of units.