An integrated and visual method has been proposed for analyzing and evaluating performances of thermal systems comprehensively in this study by coupling EXCEM (Exergy, Cost, Energy and Mass) model and MFM (Multilevel Flow Model). Tools and technologies of computer science and software engineering have been use to materialize the method. The feasibility and promising application possibility of this proposed method has been demonstrated by the findings of studying performances of a typical High Temperature Gas Rector (HTGR) cogeneration system from thermodynamic and economic aspects comprehensively as an example.