Real world clinical diagnosis and treatment activity is a complicated decision-making task. The effective clinical cases of traditional Chinese medicine (TCM) of highly experienced physicians play an important role in the routine diagnosis and treatment and the formulation of medical knowledge . Based on TCM electronic medical record data, this paper proposed a decision support prototype system on TCM clinical diagnosis and treatment based on TCM effective clinical cases and case-based reasoning (CBR) algorithm, which is used to assist inexperienced clinicians to make more reliable clinical decisions, and thereafter to improve the clinical curative effectiveness. The system integrates TCM clinical cases data set from a TCM clinical data warehouse, and retrieves the similar cases based on CBR method. In particular, according to the underlying personalized diagnosis and treatment for patients in TCM, this system implemented a flexible diagnosis and treatment modification mechanism based on correlation analysis among symptoms, diagnoses (syndrome or pattern in TCM) and medicine. Finally, through a demonstration of clinical application, we made an initial evaluation of the usefulness and practical effects of the system.