The 1,000 kt/a ethylene plant in Dushanzi adopts front-end deethanization and front-end hydrogenation process, and isothermal tubular reactor is selected for C₂ hydrogenation process. The reactor has the advantages of long operation cycle and service life, good catalyst selectivity, and basically no or little green oil produced, but it has the operation characteristics of long start-up time and great difficulty. The plant was started up with new catalyst after four rounds of overhaul, and four risks existed in the start-up with new catalyst were identified including reactor pressurization and filling operation, methanol boiling control, CO concentration control and operation adjustment for on-spec acetylene at outlet. According to the identified risks, some mitigation measures were implemented and the start-up operation mode was fixed to ensure the safety and efficiency during the start-up of C₂ hydrogenation reactor and reduce the production of off-spec ethylene products.