Abstract: Objective To investigate the current situation of mental workload of nurses in emergency department in the process of dealing with major public health emergencies，and to analyze the latent potential profile and explore its influencing factors. Methods From December 2022 to January 2023，the emergency department nurses in 9 general hospitals （5 tertiary hospitals and 4 secondary hospitals） in Zhejiang Province were selected by convenience sampling method，and the survey instruments included self-designed general information questionnaire， NASA task load index scale，psychological capital questionnaire，and general health questionnaire. Results 466 questionnaires were distributed and 456 were returned with an effective rate of 97.85% . In the process ofresponding to majo r public health emergencies，the total score of 456 emergency department nurses’ mental workload was （91.25±11.75），the total score of Psychological Capital Questionnaire was （100.08±13.89），and the total score of General Health Questionnaire was （2.34±2.90），and the latent profile analysis classified them into 4 catego- ries，which were named according to the category characteristics as C1 low load feeling and high self-evaluation （10.1% ），C2 high load feeling and high self-evaluation （24.1% ），C3 medium load feeling and medium self- evaluation（37.2%），C4 high load feeling and low self-evaluation （28.5%）. Ordered multi-categorical Logistic regression showed that age，years of work，education，hospital grade，mental health，and psychological capital were factors influencing the psychological load of emergency department nurses in coping with major public health emergencies. Conclusion The Mental workload of emergency department nurses in response to major public health emergencies is at a high level，and the psychological health of the high load feeling and low self-evaluation group is at high risk and should be a major concern. Psychological capital is negatively correlated with psychological load. This suggests that nursing managers should develop targeted interventions to improve their psychological capital，so as to reduce the high psychological load of emergency department nurses in response to major public health events.

Key words: Mental Workload, Psychological Capital, Mental Health, Emergency Department Nurses, Latent Profile Analysis