Abstract: The original design plan and the optimum design scheme of the SECCO cracking furnace chamber was numerically simulated using CFD software with suit mathematical model. Detailed information of flow field，fuel combustion and flue gas temperature field in the cracking furnace chamber was obtained，which revealed the interaction and characteristics of flue gas flow，combustion and heat transfer process in the furnace. The simulation results showed that the temperature gradient was larger，the heat distribution was uneven and high-temperature zones existed in the original design plan based on bottom burner. While in the optimum design scheme based on bottom and side wall burner，the temperature gradient was smaller and more uniform heat distribution was provided，which is beneficial to the uniform heating of the reactor tubes.