Objectives : Suicide is a serious sentinel event in healthcare organization. Suicide and suicidal attempt are fatal and long lasting mental and physical damage to themselves, family, and medical staffs. To develope the system to prevent suicidal accident in hospital, we reviewed and analysed one case of suicidal sentinel event. Methods: The risks of suicidal sentinel event were evaluated and analysed through the root cause analysis and failure mode effects analysis. Result: We found several root causes such as initial assessment of oldest patient and security issues. Couple of action plans to fix the problems were done immediately. According to failure mode, we evaluate the risk priority number to modify the action plans. Conclusion: To reduce the risk of sentinel events, we reviewed the suicidal event and established the new system and action plan to prevent sentinel events.