Abstract: The protective coating of Ni-Cr-C was obtained by adding Cr particles with different concentrations in the electrodeposition process of Ni-C. The optimization effect of Cr particle concentration on the performance of protective coating of Ni-Cr-C was analyzed, and the surface hardness of the coating was measured. The results show that the smooth Ni-C coating is formed, and most areas are in regular polygon shape. After Cr particles are added, some random nodular microstructure is formed in the surface area, and a large number of pores are generated. After increasing the Cr particle size gradually, smaller pores are formed on the coating surface.When the content of Cr particles increase, Ni diffraction peaks with different highest intensities are formed in the coating, which changes from the original(110) crystal plane to(101) crystal plane.When the Cr content increases, smaller Ni grains are formed, and the outer diameter of Ni grains reaches 29.2 nm with the addition of 80 g/L Cr particles.Stricter coatings can be prepared by adding Cr particles, and the hardness of the deposited layer increases with the increase of Cr content.The hardness of Ni-Cr-C layer is 551 HV when the content of Cr particles is higher.