The Safety-critical systems are widely used in industry. The first task of Safety-critical system design is to identify system hazards. However, the commonly used methods of system potential hazards identification have limitations in expression, creativity, etc. Based on the Misuse case(MUC), this article puts forward a kind of method of system hazard identification, which is easy to use. This approach helps system engineers to acquire system potential hazards in system requirements phase. First of all, you must acquire MUC based on the system function. Then, the textual misuse cases(TMUC) template is used to analysis the hazard of each MUC. Finally, the potential hazards in the system are obtained.