Aim This study aims to examine the relationship between professional identity and job satisfaction and their impact on intention to stay among clinical nurses in China during the prolonged COVID-19 pandemic. Methods A cross-sectional survey was conducted from April 30 to May 25, 2021, in China. Data were collected using professional identity, job satisfaction, and intention to stay questionnaires from 1425 clinical nurses. A single mediation analysis was utilized to test the interrelationship among the variables, and the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist as a reporting guide. Results Nurses indicated a medium level of professional identity, job satisfaction, and intention to stay, with mean scores of 3.85, 3.25, and 3.47, respectively. The professional identity displayed positive indirect effect on nurses' intention to stay through job satisfaction (indirect effect = 0.498, 95% CI [0.439, 0.558]). Conclusion Cultivating professional identity among nurses can increase their job satisfaction and ultimately enhance the intention to stay in the nursing profession. However, this study also suggests paying more attention to job satisfaction to keep nursing retention. These may be helpful to retain the nursing workforce.