Objective To explore the mediating role of psychological security and proactive behavior on the relationship between error management climate and patient safety competency. Methods A total of 782 nurses were selected using convenience sampling,and surveyed using a general information questionnaire, the Error Management Climate Scale (EMC), Psychological Security Questionnaire (PSQ), Proactive Behavior Performance Measures Scale (PBPMS) and Patient Safety Competency Self-rating Scale of Nurses (PSCSSN). Results The average EMC, PSQ, PBPMS and PSCSSN scores were (70.28±11.93),(61.21±13.44), (37.60±7.33) and (121.31±19.51) respectively. There were significant differences in patient safety competency scores among nurses with different professional titles, educational backgrouds and working departments (all P＜0.05). Psychological security and proactive behavior were the mediating variables between error management climate and patient safety competency. The chain mediating effect accounted for 26.14% of the total indirect effect. Conclusion Error management climate can directly affect nurses′ patient safety competency and have an indirect effect on patient safety competency through psychological security and proactive behavior. Managers should create a positive atmosphere for error management, give nurses more psychological security in patient safety management, stimulate proactive behavior, and constantly improve nurses′ competence level of patient safety.