Abstract: The hot spot temperature of oil-immersed transformer winding is an important factor affecting the aging of material insulation. Based on the electrical and structural parameters of the oil-immersed transformer, a 3D equivalent simulation model of the transformer was established, and the loss values of each wall of the oil tank are accurately obtained by calculating the magnetic field. Moreover, the traditional equivalent model and porous medium equivalent model were used to calculate the flow field-temperature distribution of the two equivalent models, and the simulation results of the transformer temperature field were obtained. The temperature distribution of the core and winding of the oil-immersed transformer and the flow velocity around the transformer were obtained. Furthermore, in order to reduce the loss caused by leakage flux on the tank wall and reduce the overall temperature rise of the transformer, electric and magnetic shielding plates were applied to the tank wall, respectively, and the influence of the two types of shielding on the tank wall loss value was calculated. According to the calculation results, the shielding effect of magnetic shielding was better, and the shielding position was further studied. According to the calculation results of the temperature field, the characteristic points in the middle of the tank wall and the bottom oil temperature, which have strong correlation with the winding temperature, are determined. The results show that the selection of the bottom oil temperature feature points is not only small in number, but also easy to achieve in large transformers, and the correlation coefficient of predicting the winding hot spot temperature is more than 0.95, and the prediction accuracy is higher. This study provides a theoretical basis and technical support for real-time monitoring of hot spot temperature in oil-immersed transformer windings.