Objective：To develop a forensic medical expert system assiting crime scene investigation. Methods：NET development platform was taken as the basis；methods of knowledge aided design system（KADS） was used，and the domain knowledge was classi－fied into three levels：domain，inference and task. The data base was constructed with SQL SERVER. The ontology knowledge base was constructed with PROT?魪G?魪. The core of inference model was constructed with CLIPS. LOADRUNNER was employed to analyze the system in order to refine and improve the database and inference mechanism. Results：The forensic expert system can produce in－structive opinion through gathering information from the scene and autopsy outcome. By simulating inference，the system can provide ideas related to cause of death，death time，manner and nature of death. Furthermore，the system can provide consultation on the num－ber of suspects and manner of a crime. Conclusion：The expert system can provide obejctive opinions for practical work. It also can manifest the truth and the crediblily of evidences. Moreover，it can provide simulation training program for forensic medicine students.