The C₃ hydrogenation cooler (E-5211) of an ethylene plant was put into operation after the overhaul in May 2015. After 18 months of operation, the tube bundle leaked, so the plant was forced to change the process flow, and the MD and PE could not be hydrogenated to propylene as normal, leading to the loss of a large amount of C₃ components and the decrease in propylene production, and seriously affecting the economic benefits of the plant. In view of the leakage of the heat exchanger tube bundle, eddy current testing technology was adopted to detect the tube bundle. The wall thickness loss of the tube bundle was evaluated based on the data and images of far-field eddy current testing, and the inspection and preventive measures for overhaul were put forward. The test results showed that the heat exchanger tube bundle has large areas of thinning and pits, which cannot meet the requirements of long-term operation of the plant, and further protective measures are needed to ensure the safe and stable production. This is also the validation application of far-field eddy current testing technology in equipment performance evaluation of megaton ethylene plant.