On the design issues of power-plant layout engineering, it frequently occurs that objective functions or criteria mutually conflict one another in terms of cost, robustness or delivery time. To this end, we are now developing a concept design support system that is used for plant-layout planning comprehensively by a flexible human-machine communication and multi-objective optimization algorithm. This design approach is based on ‘Shinayaka Systems Principle’, which advocates reactivity, adaptivity and flexibility. In this paper, we discuss the outline of plant-layout planning for power-generating plants, and evaluate suitable multi-objective optimization algorithms including Satisficing Trade-off Method. As a typical example, we apply this method to the model case of combined cycle power plats that are quite popular as an EPC (Engineering, Procurement & Construction) project.