Abstract: In the two expansions of an ethylene plant, the C₂ system of cold section was changed from the acetylene hydrogenation of the total deethanizer overhead effluent to the hydrogenation of the net C₂ product in the first stage, where only a few modification of the acetylene hydrogenation, green oil absorber and ethylene drying sections was required, and then to cascade hydrogenation of both total effluent and net product in the second stage to overcome the difficulty in refrigerant services. The plant capacity was increased twice by 60%, and the revamping work was reduced to some extent and the operation stability of system was improved.