Abstract: The operating conditions of transformers are the key factors determining their thermal life, and also play an important role in their overall life. The article explores the prominent problem of poor cooling performance of existing oil immersed self cooling methods under high temperature and heavy load conditions. From the perspectives of thermodynamics and fluid mechanics, a refined thermal fluid coupling model is established, and a multidimensional optimization design scheme for the cooling system is proposed, aiming to reduce transformer oil temperature and winding temperature, improve heavy load capacity and operational reliability, and extend equipment service life, thereby promoting transformer energy efficiency improvement and intelligent operation and maintenance.