Abstract: In order to reduce the hot-spot temperature and internal temperature rise of oil-immersed power transformers under low-frequency operating conditions, an optimization analysis is carried out for the winding-area oriented structure of low-frequency transformers based on the multi-physical field coupling of electromagnetic-thermal-fluid fields. Through the finite element numerical analysis of the electromagnetic part of the transformer, the difference between the magnetic density distribution and loss characteristics of the low-frequency transformer and the power-frequency transformer under the same working condition in the core and winding area is determined. And on this basis, the loss of the core and winding as a heat source is substituted into the fluid field and temperature field for simulation analysis to obtain the temperature and oil flow distribution of the transformer as a whole and the winding region locally. Finally, by constructing the oil flow and heat transfer model in the winding region of 20 Hz low-frequency transformer and combining it with finite element simulation, the influences of the number and distribution of oil guiding baffles on the oil flow, average temperature and hot-spot temperature in the winding region are investigated, and the optimal distribution scheme of the guiding structure is obtained. The results show that the hot-spot temperature in the winding region of the 20 Hz low-frequency transformer decreases by 14.44% compared with the model without oil baffles, which provides an optimization scheme for the compact design of the low-frequency transformer.