Objective To study the psychological state，the psychological journey and post-traumatic growth experience of emergency department nurses going through public health events of infectious diseases，of nurses，so as to provide guidance for psychological interventions and subsequent training for emergency department nurses. Methods Using a rooting theory research approach，in-depth interviews were conducted with emergency department nurses involved in COVID-19 frontline ambulance work between December 2022 to January 2023 while the researcher conducted full participant observation to observe the work status or emotions of nurses，teamwork and cooperation，and handling various unexpected situations. The data was analyzed using Strauss and Corbin’s rooting theory. Results The stress response of emergency department nurses when faced with a public health event of an infectious disease was divided into four phases：stress，fatigue，debugging and growth，forming four categories，13 sub- categories and 20 codes. Conclusion The psychological reaction of nurses in emergency department when they face public health events of infectious diseases is a one-way dynamic change process. Stable social support and the responsibility and protection of managers are the important driving forces for nurses to change from stress fatigue to debugging growth. Good professional quality，high resilience of psychological traits and reflection sublimation are the internal factors that promote growth. It is suggested that department managers should make emergency response when dealing with public health events of infectious diseases，improve procedures and systems，create a positive department atmosphere，carry out specialized training，consolidate professional knowledge and skill reserves，and pay special attention to the shaping of necessary psychological qualities.