The corrosion of convection tubes in ethylene cracking furnace is introduced in this paper. The appearance of corrosion leakage location, furnace tube material, metallography, microstructure and scale layer are inspected. The causes of corrosion are analyzed based on the inspection results. It is concluded that the corrosion leakage is resulted by the condensate in convection section and the sulfur element in naphtha, and some measures for operation optimization and process modification are proposed.