Abstract: Aiming at the excessive temperature rise of 35kV main transformers in petrochemical enterprises, this paper takes on-line monitoring as the basis, and analyzes the main causes from two aspects of heat generation and heat dissipation. On this basis, the data obtained from distributed optical fiber temperature measurement and other monitoring methods are used to analyze the specific laws of temperature rise caused by influencing factors such as load characteristics. Furthermore, a comparative model is established, the operating conditions and cooling device setpoints are adjusted, and reasonable load adjustment measures are proposed, so as to form the main transformer temperature rise control and operation optimization measures suitable for petrochemical working conditions. The practical engineering project verifies that the above measures can keep the top oil temperature rise of the main transformer below 55K and the average winding temperature rise below 65K, which improves the operation safety and stability of the main transformer as well as the continuous reliability of power supply.