Abstract: Outdoor box capacitors often encounter problems such as uneven temperature, water leakage at the inlet and outlet, and dust blockage in traditional left and right ventilation and heat dissipation methods in rainy, snowy, cold, or high-temperature environments. A heat dissipation scheme for side inlet and top outlet air is design based on the internal configuration and heat dissipation requirements of box capacitors. By optimizing the number and position of air inlet and outlet, fans and installing guide plates at the air inlet, the internal components meet the heat dissipation requirements at an ambient temperature of 55 ℃, and the box body meets the structural protection requirements of IP54. The actual operation effect of this scheme is good, providing a reference for the heat dissipation design of box capacitors.