Objective:To explore the motivation of the formation of the breastfeeding mission and education behavior of nurses in NICU, analyze the deep reasons, and construct the motivation and path theoretical model of the formation of the breastfeeding mission and education behavior of nurses in NICU.Methods:Through semi-structured interviews, the qualitative research method of grounded theory was used to study 20 nurses in the Second Affiliated Hospital, University of South China from July to September 2020, to construct the motivation and path theoretical model of the formation of the breastfeeding mission and education behavior of nurses in NICU.Results:The research identified five main categories: attitude factor, ability factor, behavior factor, internalization and externalization. Under the influence of three dimensions of attitude level, ability level and behavior level and their cross-layer interaction effects, the NICU nurses were driven to form stable breastfeeding mission and education behaviors through internalization and externalization.Conclusions:Based on the evolutionary context of "multi-dimensional factors and their interaction drivers-internalization-externalization", the relationship between attitude factors, ability factors, behavioral factors, internalization, and externalization are clarified. It provides a theoretical reference basis for managers in managing the breastfeeding propaganda and education of nurses in the NICU, and enriches the theoretical framework of breastfeeding behavior in the NICU.