Abstract: The secondary filter screen is an important structural component for filtering seawater impurities in the condenser, with a vertical cylinder structure, and there are fixed filter plates, K-frames, partitions and other components inside. At present, sacrificial anodes are used in nuclear power plants to protect the secondary filter, and according to external experience feedback, when the sacrificial anodes and fasteners fall off, they will impact the titanium tube in the condenser or enter the titanium tube to block to form foreign matter, and there is a risk of damaging the titanium tube and causing the power reduction of the unit. In order to eliminate the above risks, the feasibility of two improved protection methods, sacrificial anode displacement or applied current cathodic protection in the secondary filter, was evaluated by combining numerical simulation software and site investigation, and the protection mode of the secondary filter to ensure the safe and stable operation of the nuclear power plant unit was optimized. The results showed that when the sacrificial anode was moved to the upstream of the secondary filter screen, when the sacrificial anode of the cylinder was symmetrically distributed on both sides of the secondary filter screen and the anode position was consistent with the center position of the secondary filter screen, the secondary filter screen had the best protection effect. An impressed current cathodic protection system was installed upstream of the secondary filter screen plate. When the auxiliary anode was in the same position at the center of the secondary filter screen and was 1.2 m away from the center of the cylinder, the secondary filter screen was protected best.