Abstract: The wellhead using the Steam Assisted Gravity Drainage (SAGD) technology is an important heavy oil thermal recovery device in Xinjiang Oilfield. However, it has experienced erosion and thinning with the increase of service time, laying a significant impact on safe production due to the hidden dangers. In order to discover the corrosion and thinning parts of the thermal recovery wellhead device in time, the signal characteristics of different detection conditions were analyzed through finite element simulation, and the results were verified by test pieces containing simulated corrosion defects. The experimental results show that the electromagnetic ultrasonic testing method proposed in this paper can effectively find the corrosion defects of heavy oil thermal recovery wellhead equipment. This article has guiding significance for the development of electromagnetic ultrasonic high temperature online detection process and on-site detection.