The invention discloses a cathode frame for an electrostatic precipitator. The cathode frame comprises a rectangular frame formed by four cross rods and five vertical rods. The cross rods and the vertical rods are perpendicular to each other and are located in the same plane, the four cross rods are arranged in parallel with one another, and the five vertical rods are arranged in parallel with one another. The longitudinal length of the rectangular frame is divided into trisections by the four cross rods, the transverse length of the rectangular frame is divided into 2: 1: 1: 2 by the five vertical rods, and one vertical rod is located on the perpendicular center line of the rectangular frame. Upper sections of two vertical rods on the outermost side of the rectangular frame are vertical reinforcing rods, and each vertical reinforcing rod is provided with two horizontal through holes used for installing supports of the cathode frame. The cathode frame for the electrostatic precipitator is simple in structure and convenient to assemble, the situation that the cathode frame for the electrostatic precipitator is prone to bending deformation even integrally sliding down and collapsing from a main cathode supporting frame can be effectively avoided, and safety and stability of electrostatic precipitator operation are greatly improved.