The present disclosure discloses a preparation method of a multi-functional marine engineering alloy. Through the coupling of a multi-principal alloy structure, structural entropy, and temperature and powder metallurgy and heat treatment, mutual solubility between elements and free energy of an alloy system are regulated, Cu grain boundary segregation is eliminated, and uniform and dispersed nano-precipitation of the anti-fouling element Cu in corrosion-resistant and high-plasticity multi-principal alloys is realized. The preparation method is simple and controllable to operate, and the prepared material has plasticity higher than 75%, high yield strength, excellent corrosion resistance and anti-fouling property, and has important application prospects in the field of marine engineering.