In order to improve the corrosion resistance of Q235 steel in seawater and to prolong its service life in marine environment, Ni-based/WC composite cladding layer with different mass fraction CeO2 was prepared on Q235 steel by laser cladding technology. The microstructure, microhardness, and electrochemical corrosion properties in NaCl solution (mass fraction of 3.5%) of the coatings were characterized by using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, microhardness tester, and electrochemical workstation, respectively. The results show that the addition of an appropriate amount of CeO2 promoted grain refinement and a uniform distribution of the microstructure, thereby enhancing the hardness and corrosion resistance of the coatings in NaCl solution. When the mass fraction of CeO2 adds reached 1%, the coating exhibites the highest average hardness and the best resistance to seawater corrosion. This study provides a theoretical reference for subsequent laser cladding preparation of coatings resistant to seawater corrosion.