Abstract: A cobalt-based alloy laser cladding layer was prepared on the surface of 300M ultra-high-strength steel using electromagnetic-assisted laser cladding technology. The macromorphology, microstructure, mechanical properties and wear resistance characteristics of the cladding layer under different electromagnetic states were studied. The results show that the external electromagnetic field can change the morphology of the cladding layer and reduce the crack sensitivity. Compared with the coating prepared without the assistance of a magnetic field, the grains of laser cladding prepared under the action of electromagnetic recombination are refined, which can improve the hardness of the cladding layer. The comprehensive mechanical properties of the cladding layer prepared under the magnetic field parameter of 30 m T magnetic induction intensity and 100 A current parameter are best. Under the effect of a magnetic field, the elastic modulus of the cladding layer is significantly reduced, thereby improving the ability of the cladding layer to resist the plastic deformation during wear, thereby improving the wear resistance of the cladding layer. This study provides a theoretical and experimental basis for preparing a high wear-resistant protective layer on the surface of ultra-high-strength alloys.