Abstract: The preparation method of the metallographic test sample of nickel coating on cobalt block was mainly studied. The effects of inlay method, inlay material and sampling method on the quality of metallographic test sample were discussed. The results show that the quality of hot inlay coating sample was good.The quality of the metallographic test sample embedded with bakelite powder with edge protection was the best. It was easy to make the coating fall off by cutting the coating sample with electric spark line cutting, and the integral mosaic method could avoid this phenomenon. The best preparation scheme for the metallographic test sample of nickel coating on cobalt block was to adopt the integral hot inlay method of common bakelite powder with edge protection.