Objective To explore the impact of "knowledge-attitude-practice" (KAP) training mode on head nurses’ core competency in healthcare-associated infection (HAI) prevention and control in a tertiary first-class general hospital. Methods Head nurses of 113 departments in a tertiary first-class general hospital were taken as the research objects. Guided by problems and demands, HAI training was conducted using the KAP training mode. The training was divided into two stages: a stage with problems of infection control and investigation of knowledge demands, as well as a stage with KAP training mode implementation. It included theoretical lectures, visits and lear-ning, and supervision on rectification. Scores of theory, supervision, and core competency of head nurses before training, 1 month and 6 months after training were compared by the analysis of variance. SPSS 26.0 statistical software was used for analysis. Results The top three infection control problems in this hospital were hand hygiene, prevention and control of infection with multidrug-resistant organisms, as well as HAI prevention and control in the wards. The top three training modules required urgently by the head nurses were occupational exposure and self-protection, principles of medical waste disposal, as well as prevention and control of HAI in the wards. Both scores of theory and supervision after training were higher than those before training, with statistically significant diffe-rences (both P<0.01). The core competencies of the head nurses were at a high level. After implementing KAP training mode, the scores of dimensions in critical thought and research, clinical nursing, leadership, and profe-ssional development, as well as the overall score of core competencies were all higher than before training. Diffe-rences were all statistically significant (all P<0.05). The overall scores of dimensions in legal and ethical practice, education and consultation, as well as interpersonal relationship were all higher than before training, but the diffe-rences were not statistically significant (all P>0.05). Conclusion KAP training mode can significantly improve the scores of theory, supervision, and core competencies of head nurses, and can be further promoted and applied in head nurses’ infection control training.