The technology to deposit diamond coatings on cemented carbide powder by using electro-phoretic deposition method was investigated. The effect of the mass fractions of cemented carbide and MgCl
2·6H
2O on the quality of the coating was studied, and the prepared powders were characterized. When the masses of the cemented carbide powder, the diamond powder and MgCl
2·6H
2O were 28.0 g, 4.0 g and 1.0 g, respectively, the prepared diamond coating was uniform and good in density.