Objective:To investigate the level of nurses' turnover intention in ClassⅢ Grade A hospitals, and explore the correlation and interaction between nurses' psychological capital, social support, and turnover intention.Methods:Totally 2 600 nurses from 3 ClassⅢ Grade A hospitals in Urumqi were selected for questionnaire survey with the general demographic information questionnaire, Psychological Capital Questionnaire (PCQ) , Social Support Scale (SSS) , and Turnover Intention Scale (TIS) between January and August 2018. Totally 2 345 valid questionnaires were recovered. The structural equation model was used to analyze the mediating effect of nurses' psychological capital in the path of social support and turnover intention.Results:The total scores of 2 345 nurses' psychological capital, social support, and turnover intention were (86.30±8.99) , (41.17±7.68) , and (14.39±3.63) , respectively. The correlation analysis showed that nurses' social support and psychological capital scores were negatively correlated with their turnover intention score ( P<0.05) . The structural equation model analysis revealed that psychological capital had a mediating effect between social support and turnover intention, and the mediating effect accounted for 38.2% of the total effect. Conclusions:Nurses in Class Ⅲ Grade A hospitals have a high level of turnover intention. Nursing managers may reduce nurses' turnover intention by improving their social support and psychological capital.