PetroChina Liaoyang Petrochemical Company completed the transformation of steam cracking unit for processing light raw materials during the overhaul in 2019. Two liquid cracking furnaces F101x and F110 were transformed into gas furnaces, and aromatics tail gas and liquefied gas were introduced as raw materials. After the transformation, the ethylene yield was increased from 31.00％ to 35.01％ and the comprehensive energy consumption was reduced from 693.47 kgEO/t ethylene to 677.97 kgEO/t ethylene, greatly improvingthe operation level of the unit. The cracking, quenching and compression systems were affected to varying degrees. Through optimization and adjustment, the normal operation of the systems was restored.