Abstract: Electroless nickel plating was used to improve the weldability of diamond/Cu composites. Experiments were performed to study the influence of nickel plating process on the phosphorous content of Ni-P alloy coatings as well as the effects of phosphorous content on the bond strength between the coatings and diamond/Cu substrates, the corrosion resistance of the coatings and the spreading area of AgCu28 filler on the coatings. Besides, the coating thickness and process were optimized. It is found that AgCu28 filler on the coatings with 5.8% to 8.7% phosphorus shows good spreadability, and the coating of 8.7% P has a better corrosion resistance than that with a lower P content. In comprehensive consideration with bond strength and filler spreadability on the coatings, the coating with 10 to 20 rain plating time, namely the thickness of 5 to 8 μm, is ideal.