Panel-type radiator has the advantages of low cost, simple structure and high heat dissipation efficiency. It is a key equipment to ensure the normal production of transformers and adjust the temperature of the process medium. In order to improve the heat transfer performance of the plate radiator, achieve the purpose of energy saving, environmental protection, and reduce energy consumption, heat plates are installed on both sides of the model in the Y direction, and perforations of different diameters are set on heat plates, the effect of the perforation diameter on the radiation heat transfer, convection heat transfer and comprehensive heat transfer performance of the heat plates is studied by numerical simulation. The results show that with the heat plates installed, the total heat dissipation of the radiator is increased by 3.9%, and the oil temperature at the outlet 0.3 m is reduced by 6.91 K; the comprehensive heat transfer performance of the heat plates on both sides with an aperture of 18 mm, is increased by 25.46% and 28.76% respectively, and the 18 mm perforated heat plate is the best choice. A new empirical understanding is provided for the improvement and design of the external structure of panel-type radiator.