Abstract: Objective: To analyze the root cause of aggressive behavior in male psychiatric patients, and to provide the evidence for targeted prevention measures. Method: Totally 87 cases of attacks occurred in male psychiatric patients from January to December, 2014 were selected to investigate. Root Cause Analysis (RCA), consisting of five aspects (individual,machine, material, method, and environment) was used to analyze the causes of aggressive behavior in male patients with psychosis. Results: In the 87 cases of male patients with psychosis attack behavior, each aggressive behavior was caused by system, individual and environment factors. The possibility of the attract behavior will be increased with the emerging of risk factors. Conclusion: We should strengthen the safety consciousness in nurses, and manage the situation from several aspects and multi-channel. Thus, violence caused by hospitalized psychiatric patients could be reduced.