Abstract: The naphtha end point(x) from delayed coking distillation tower is taken as the independent variable representing the depth of separation. The relationships between x and energy consumption, steam product, product distribution are examined based on the process flow sheet，using the technology of process simulation and data regression. A general method of determining the optimal x is developed, considering the total economic benefit or total energy loss. The application of the method in a 4.2 Mt/a delayed coker can improve the benefit of the unit about 7.679 million Yuan/a.