The invention discloses a cathode for an electrolysis mechanical combined machine tool. The cathode comprises a column-shaped basal body, wherein the basal body is provided with an axial center hole; at least two axial imbedding grooves are uniformly distributed on the surface of a cylindrical lower part of the basal body; the imbedding grooves extend to the bottom surface and intersect with each other; sintered diamond strips are adhered in the imbedding grooves; the height of the sintered diamond strips exposed out of the surface of the basal body is 0.05 to 2 mm; axial liquid spraying tanks which are uniformly distributed and run through the axial center hole are arranged on the surface of a cylindrical lower part of the basal body; the liquid spraying tanks extend to the bottom surface; and the width of the liquid spraying tanks is 0.25 to 0.35 mm. The cathode for the electrolysis mechanical combined machine tool provided by the invention adopts gaps to spray electrolyte, so the electrolyte is uniformly supplied, the removal quantity of workpieces is also uniform, and the cathode is suitable for fine machining. Because the height of the sintered diamond exposed out of the surface of the basal body is relatively high, no electric spark is generated during electrolytic machining, and the service life of a diamond tool can be greatly prolonged and the sharpness of the diamond tool can be greatly improved.