As an methodology for promoting the quality and efficiency of health care, clinical decision support systems (CDSSs) have gained much improvement. The knowledge base (KB) plays an important role in DSS. For CDSSs, the construction of KB means modeling the medical knowledge based on a suitable model. This study analyzes the SAGE model, then implements it on knowledge of diagnosis and treatment of Metabolic Syndrome (MS), and improves the SAGE to enhance its expression ability. The model is constructed as the KB in CDSS, and be applied in hospital. The evaluation result of CDSS reveals that the SAGE model should be useful in clinical application. Finally, this study propounds some points yet to be improved in the SAGE.