The invention discloses a cracking furnace. The cracking furnace comprises a convection section, a radiation section communicated with the convection section, a quenching boiler and a steam drum, wherein the convection section is internally provided with a convection tube bundle communicated with a feed inlet of the cracking furnace; the steam drum is arranged on the top of the convection section;the top of the convection section is provided with a fan communicated with the cracking furnace; the radiation section is internally provided with a plurality of groups of radiation tube bundles; theradiation tube bundles comprise a plurality of radiation furnace tubes; the plurality of radiation furnace tubes are arranged along the peripheries of the radiation tube bundles at intervals; the radiation furnace tubes are communicated with the convection tube bundle; the bottom and sidewall of a hearth in the radiation section are separately provided with a plurality of combustors; and the outlet ends of the radiation furnace tubes are communicated with the quenching boiler. According to the cracking furnace provided by the invention, through improvement of the arrangement mode of the radiation furnace tubes, difficulties in arrangement of the radiation furnace tubes can be reduced, and reaction conditions in each group of radiation furnace tubes in the cracking furnace are maximally maintained same; and the cracking furnace has the advantage of a small occupied land area under the condition of same unit production capacity.