The invention provides a power distribution ring main unit with good dehumidification and ventilation effects. The power distribution ring main unit comprises a ring main unit, a first hollowed-out plate, a second hollowed-out plate, a ventilation cooling cavity, an electrical equipment fixing cavity, a fixable damp-proof supporting frame structure, a maintainable air blowing box structure, a slidable cooling electrical equipment fixing frame structure, an insertable heat dissipation protective cover structure, a hollowed-out bottom plate, a heat dissipation cavity, a stainless steel filter screen, a cabinet door, an observation window and a door handle; the first hollowed-out plate is in bolted connection with the lower part of the inner wall of the ring main unit; the second hollowed-outplate is in bolted connection with the upper part of the inner wall of the ring main unit. L-shaped support frames, a spacing plate, support rods, a first fixed net, an activated carbon adsorption net, a second fixed net, the ring main unit and the hollowed-out bottom plate are adopted, the moisture adsorption work on gas entering the ring main unit through the activated carbon adsorption net inthe use process is facilitated, and the moisture is prevented from entering the ring main unit to corrode electrical equipment.