PURPOSE: To attain the application of plant design support system to the functional layout design and the simulation of an optimum operation plan for a plant positioned in an upstream process of the plant designing by producing a model for optimization of the plant operation which is layed out from the plant design information that is layed out by a parts data base and a visual tool.

CONSTITUTION: A visual tool 2 which lays out a plant designs a plant based on a parts data base 1 of the plant. A design information extracting means 3 extracts the design information including the structure parts of the plant and the connection information on these parts out of the layout result of the plant. Then a means 4 produces a model for optimization of the plant operation based on the design information on the plant layout and by means of a plant designing knowledge data base 5. In the case of a heat supply plant, for example, a load balance model, a plant input/output action model, etc., are produced. The a means 5 optimizes the plant operation to minimize the energy cost, etc.