The cracking performance of ethylene plant was evaluated based on the design indexes and production data of cracking raw materials (naphtha and hydrogenated tail oil) in Fushun petrochemical ethylene plant. Firstly, the component, physical parameter and cracked gas composition of ethylene cracking feedstock were measured, and then the decomposition temperature, dilution ratio, pace time, cleaning cycle, oil price and fragmentation depth were compared. At the same time, the influence the properties of pyrolysis raw materials on the product yield was examined. The last step was to make a comparison between manufacturing data and design indicator, and to propose some concrete measures to optimize its system. The results demonstrated that the physical property indexes of naphtha and hydrogenation tail oil were within the range of allowable design, but their cracked gas yield exceeded the design value. The total yield of ethylene, diene, methane and hydrogen derived from cracking naphtha was 4.57% higher than the result of crackers originated in hydrogenation tail oil. The yield of ethylene and diene showed 0.44% and 0.63% rise respectively. However, C4, C5, C6-C8, C9 and fuel oil from cracking naphtha had relative lower yield (5.18%) in contrast to those from cracking hydrogenation tail oil.