It is feasible for the grassroots design and retrofit design of the heat exchanger network(HEN) to enhance the efficiency of energy utilization for process industries.In order to realize the comparison of these two methods,the mathematical models with the objective function of cost were built on the base of the stepwise superstructure.The developed hybrid genetic algorithm was employed to solve them.The comparisons were done from the aspects of energy saving,capital cost and payback period of these two methods.The results demonstrate that the retrofit design is little worse than the grassroots design in energy saving,but much better in capital cost and payback period obviously by the way of reusing of existing heat exchangers.