Aim:This study aims to measure and understand the professional identity of nurse practitioners and investigate the impact on job satisfaction and intention to stay during the prolonged COVID-19 pandemic.Background:The two years of the prolonged COVID-19 pandemic have impacted the nursing profession by altering the nursing role,work environment,and public recognition,which inevitably challenge nurses’ professional identities.The nursing professional identity is important because it leads individuals to think,feel,and act like professional nurse who commits to patients and families.Nurses with a higher professional identity are associated with better job satisfaction and intention to stay.Besides,there is a relative paucity of research into professional identity among clinical nurses in the pandemic era.Some research discovered that nursing professional identity increased during the initial period COVID-19 outbreak.However,most studies used a quantitative or qualitative design only without exploring the impact of professional identity on nursing.There is no study that captured the dynamic of professional identity and how it impacts nursing job satisfaction and intention to stay during the prolonged COVID-19 pandemic.Method:A mixed method sequential explanatory study was undertaken to address the study’s research questions,consisting of two distinct phases:the quantitative,ordinal data is collected and analyzed first,followed by the qualitative,textual data,which helps explain or elaborate on the quantitative findings obtained in the first phase.The quantitative data in this study assisted in determining the level of professional identity and its relationship to the intention to stay and in purposefully selecting respondents for the second phase.The four questionnaires were used in the quantitative phase:（1）demographic questionnaire,（2）The professional identity scale,（3）Chinese Nursing Job Satisfaction Scale（NJSS）,（4）Intention to stay scale.The final responses were 1425 from 2434 nurses,representing a response rate of 58.5%.The IBM SPSS statistics 26 with the significance level at p＜0.05 or p＜0.001 was used to run the independent sample t-test,analysis of variance and the Pearson correlation analysis.Moreover,the PROCESS macro version 3.5 model 4 was adopted to analyze one independent variable（professional identity）,one dependent variable（intention to stay）,and one mediator（job satisfaction）.In the second phase,29 respondents involved in nine interviews and four focus group discussions approach to understand more about professional identity tested in the first phase,also elaborated its influencing factors.Data analysis process utilized Colaizzi’s method and was carried out as a team activity and all transcribed interviews were imported into the Quirkos software package2.4.1 for easy coding and retrieval to identify the emerging themes.Findings:In the quantitative stage,this study revealed that the nurse’s professional identity,job satisfaction,and intention to stay were scored of 3.85,3.25,and 3.47 respectively.The professional identity was significantly associated with job satisfaction（r=0.712,p＜0.001）and intention to stay（r=0.424,p＜0.001）.While in the mediation analysis,professional identity showed indirect effect on intention to stay through job satisfaction[Total indirect effect=0.498,95%CI（0.439,0.558）].In the qualitative stage,seven themes and some sub themes emerged.Four themes related to the nurse’s perception of their professional identity:（1）Difficult but valuable;（2）A profession with skills and knowledge or a job with low education image;（3）Important and unimportant roles;（4）Changeable professional identity.Meanwhile the rest three themes displayed nursing professional identity development factors:（5）Four gaps in the professional identity development;（6）Factors contributing to professional identity;（7）Nurse action to fight for professional identity.The quantitative and qualitative stages were connected when selecting respondents for qualitative interviews and focus group discussion.The results of the quantitative and qualitative were integrated during the results.Conclusion:During the prolonged COVID-19 pandemic,professional identity of nurses was in the middle level,which significantly impact the job satisfaction and ultimately influence the intention to stay.Professional identity was not stagnant rather than dynamically changeable throughout nurses’ career,without exception during the pandemic.The influencing factors of professional identity are discussed more in this study.Implication and recommendation are also provided.