The invention discloses a power distribution box for power transmission line modular design. The power distribution box comprises a power distribution cabinet body, power distribution devices are uniformly arranged in the power distribution cabinet body, and ventilation adjusting mechanisms are uniformly arranged at the vertical position of the right side in the power distribution cabinet body; heat conduction rods penetrate through the upper and lower ends of the left side in the power distribution cabinet body and are slidably connected with the upper and lower ends of the left side in the power distribution cabinet body, a contact adjusting mechanism is fixedly connected to the end, located in the power distribution cabinet body, of each heat conduction rod, and an air rod is fixedly connected to the left side in the power distribution cabinet body and located at the side, close to the middle, of the heat conduction rod; a corrugated blocking piece is movably connected into the right side of a storage supporting plate, a contact pressing piece is fixedly connected to the vertical position of the right end of the corrugated blocking piece, and the end, located outside the power distribution cabinet body, of the heat conduction rod is uniformly and fixedly connected with the distributed heat dissipation rods. The invention relates to the technical field of power transmission lines, and according to the power distribution box for the power transmission line modular design, the air environment of the power distribution devices at the upper and lower positions is blocked, the heat conducted to the air pressure part is reduced, and the overall working efficiency of the power distribution cabinet is guaranteed.