The optimal minimum temperature difference and the optimal total cost targets based on the energy and capital cost were determined before the synthesis of the heat exchanger network. The present method using the system separation, was applied to the system which have the discontinuity on the temperature-enthalpy diagram, the multiple pinches and the match constraints for the intangibles of design such as safety, layout and etc. The program based on the above method was developed and it was possible simply to find the optimal target for the actual heat exchanger network by the pinch design rule.