¡¡¡¡ Cracking furnace is the key equipment in ethylene production. We have modified ethylene cracking furnaces in Daqing£¨new and old district£©, Maoming, Fushun, Dushanzi, Jihua petroleum enterprises. The heat load of the bottom burner is increased, and bottom pre-heaters are added. The operating efficiency and control accuracy are improved, thus much energy is saved. The modification work generates great economic and social benefits.