Abstract: By modeling the combined system of gas turbine and heater, a method focusing on integrated optimization of the combined system is proposed in this paper. To an existing heater with a stipulated process heating duty, this method can be helpful for choosing the best size of gas turbine and telling the optimal operation scheme of the combined system. At the same time, detailed calculation of the heating system can be carried out to give suggestions for adjusting heater to cope with the optimal operation of the combined system. This method can also provide exergy analysis to discover the exergy loss distribution and exergy efficiency of the system. Finally, a case study on heater of an atmospheric distillation unit with a processing capacity of 12 Mt/a is performed to validate the feasibility of this method, and the result is positive. In this case, if a gas turbine with an output power of 13.43 MW is combined with the heater, the efficiency of power generation by the additional fuel consumption of the system reaches as high as 55%, and comprehensive incremental benefits of 13.68 million RMB per year could be gained.