Abstract: The fluid flow and reaction of vacuum residue in Delayed coking heater was investigated. Based on the balance of mass, heat and momentum, a mathematic model for process calculation in delayed coking heater tube was established. The temperature, pressure, composition and vaporizing fraction along axial direction of the tubes were calculated by the model. The results of calculation agree well with the data of actual operation on some delayed coking heater and are in accordance with the experience knowledge. The model can be used in different working conditions of steam injection and furnace feed fluctuation and provide theoretical guidance for the optimized design and operation of delayed coking furnace.