Circulating water filtration system (CFI) is one of the essential systems to ensure the cooling of nuclear power units, and its reliability and stability is of great significance for the safe operation of the unit. By analyzing the failures in operation control of grid cleaning machines in the circulating water filtration system of a nuclear power plant during daily operation, and considering the design problems of the system and the actual operation and maintenance circumstances, several improvement measures are put forward such as replacing the limit control equipment, modifying the liquid level gauge, and optimizing the control logic, which effectively improves the operation reliability of the grid cleaning machines, reduces the occurrence of system failures, and ensures the operation safety, reliability, and economics of nuclear power units.