Recycling decoking effluent to firebox of cracking furnace is one of the effective measures to reduce pollutant emissions from the cracking furnace, and the piping layout for recycling decoking effluent to firebox has a significant impact on the decoking effect. This article uses CFD technology to numerically simulate the piping layout for recycling decoking effluent to firebox. RNG k- ε turbulence model is used for the simulation, and the wall function Standard Wall Fn is used to correct the near wall flow. The calculation results indicate that a reasonable piping layout can ensure the even entry of decoking effluent into the firebox without affecting the normal operation. The simulation calculation based on CFD technology can accurately predict the flow of decoking effluent in pipelines, providing technical reference for the piping layout for recycling decoking effluent to firebox of large-scale cracking furnace.