Controller design based on modern control theory is rather complicated than that based on classical control theory. If we express the controller as a mirror image of the equipments (actuator, control object, detector), we can clarify the controller in a simple structure. The systematic procedure of the controller design is as follows: (1) Setting of the control objective, (2) Modeling of the control object (identification), (3) Application of control theory, (4) Characterization of the detector part and actuator part, (5) Programing, (6) Implementation of the experiment. Following the systematic procedure, the controller for OTEC (Ocean Thermal Energy Conversion) plant was designed and the control experiments of the OTEC plant were implemented. Through the experiment, some problems on adaptive control and system identification were found and a problem of bursting phenomena was solved by using a stopping-and-starting rule for an on-line identification.