To enhance the long-term performance of steel fibers in a marine environment， this research carries out surface treatment of steel fibers based on the iron-catechol biomimetic complexation reaction to improve their rust resistance. The surface treatment of steel fibers was conducted using different immersion times （1 d， 3 d and 7 d）， varying concentrations of tannic acid solutions （25 g/L， 50 g/L and 150 g/L）， and diverse treatment temperatures （25 ℃ and 55 ℃）. The effect and mechanism of rust resistance enhancement were investigated through tensile strength and surface morphology analysis. The results indicate that the biomimetic complexation reaction effectively enhances the chloride ion corrosion resistance of steel fibers by forming a dense protective film on their surface， and improves their long-term tensile strength. Through simulated exposure tests， the long-term performance evolution of surface-treated steel fibers in seawater sea sand mortar was studied. The results reveal that the iron-catechol complexation layer can still effectively protect steel fibers in an alkaline mortar environment， enhance their long-term tensile strength. Meanwhile， tannic acid surface treatment effectively improves the long-term flexural capacity and fracture toughness of steel fiber seawater sea sand mortar specimens. This research provides new design ideas for improving the durability of steel fiber seawater sea sand mortar specimens， which can be applied in marine engineering construction.