Abstract: Diamond reinforced nickel-based composite coatings were prepared by electrodeposition technology at current densities of 1, 2, 5, 10 A·dm^-2. The microstructure and wear resistance of the composite coatings were studied. The growth of nickel grains on the cathode surface was simulated by COMSOL software, and the optimization effect of diamond particles on the microstructure of the composite coatings at different current densities was analyzed. The results show that the structure of nickel diamond composite coatings prepared at current densities of 1, 2 A·dm^-2 was dense and uniform with a higher diamond content. As the current density increased, the diamond content decreased, and a pyramid structure appeared on the surface. The composite coatings exhibited an obvious 200 silk texture, and as the current density decreased, the strength of the texture and the grain size decreased. The deposition of more diamond particles at low current densities hindered the growth of nickel grains at the bottom, and the high current density around the diamond particles enhanced the refining effect of diamond on the nickel grains. Under the dry friction conditions, with the increase of current density, the stable friction coefficient and wear scar size of the composite coating increased, the abrasive wear degree increased, and the wear resistance decreased. when the current density was 1 A·dm^-2, the composite coating had the smallest stable friction coefficient and the depth and width of the wear scars; the wear resistance was the best.