Objective To explore the internal and external factors and mutual mechanisms, to construct an attribution model for successful implementation for exclusive breastfeeding behavior among first-time mothers, and to develop of targeted measures to increase exclusive breastfeeding rates. Methods Semi-structured interviews were conducted among 15 first-time mothers who had successfully implemented exclusive breastfeeding 6 month after childbirth.Then an attribution model was constructed. Results Six main categories and 13 sub-categories were identified:harvesting motivation （understanding the benefits, and understanding the drawbacks of formula feeding）, taking action （seeking help in the face of difficulties, and taking initiative to learn feeding knowledge）, internal and external regulation（improving self-efficacy, family and hospital support）, impetus for action （perceiving happiness, and actively identifying information）, achieving changes （grasping the feeding pattern, and establishing the balance between supply and demand）, maintenance （continuous lactation, long-term growth advantages, family and social support）.Then the relationship between the main and sub-categories was incorporated into the theoretical model, and finally the attribution model of primipara′s 6-month exclusive breastfeeding behavior was obtained. Conclusion Harvesting motivation is the starting point of breastfeeding, followed by taking action; internal and external regulation is the turning point after encountering difficulties.First-time mothers who gain motivation and reap the benefits of change are more likely to engage in breastfeeding behaviors for longer periods of time.