A heat dissipation device of a transformer disclosed in the invention includes a transformer case, Transformer case door, aluminum hinge, rainwater collecting device, air cooled processing chamber, anupper partition plate, a lower partition plate, a vertical partition plate, a radiating fan, an air inlet, an air outlet and a ventilation hole, one side of the transformer box body is hinged with atransformer box door through an aluminum alloy hinge movably, a rainwater collecting device is fixedly installed on the top of the transformer box body, and an upper partition plate is fixedly installed on the upper side inside the transformer box body; As that junction of the invention has good heat dissipation effect, energy conservation and environmental protection, promote the air circulationinside the transformer, The invention realizes the organic combination of air cooling and water cooling, and the rainwater collected flows and absorbs heat inside the transformer to achieve the purpose of heat dissipation. Various kinds of heat dissipation effectively improve the heat dissipation performance of the transformer, and the rainwater is used for water cooling and heat dissipation, thereby effectively reducing the energy consumption and cost of heat dissipation of the transformer, saving energy and environmental protection, and having strong practicability.