The invention provides a diamond grinding wheel bar. The diamond grinding wheel bar comprises a steel base body and a sintered sand layer, wherein the steel base body is located at one axial end of the diamond grinding wheel bar, and the sintered sand layer is located at the other axial end of the diamond grinding wheel bar. The sintered sand layer is prepared from a mixture containing diamond powder and metal powder through sintering, and the working face of the grinding wheel bar is located on one axial end face of the grinding wheel bar and located on the sintered sand layer. Specifically, the metal powder comprises powder containing copper and tin, carbonyl iron powder, chromium powder and carbon powder, wherein the mass of the copper element accounts for 55-80% of the total mass of the metal powder, and the volume of the diamond powder accounts for about 15-30% of the total volume of the sintered sand layer. According to the diamond grinding wheel bar, an available processing tool is provided for grinding sapphire panels, the machining life of the diamond grinding wheel bar is long, and the precise dimensions and processing yield of the sapphire panels are guaranteed; and in addition, the production efficiency of sapphire processing is improved, and conditions are created for large-scale production of the sapphire panels.