Objective To develop a breastfeeding-related stress assessment scale to provide effective tools for the identification, eva-luation and monitoring of breastfeeding pressure in women and to test its reliability and validity.Methods Following the process of scale development, the scale dimensions were formed based on the conceptual framework of breastfeeding-related stress, and a preliminary pool of scale items was constructed by combining the results of the previous qualitative study and literature review, and the first draft of the scale was formed after two rounds of expert consultation and cognitive interviews.A total of 950 postpartum breastfeeding women were selected for the survey.Then item analysis, validity analysis and reliability analysis were performed.Results Exploratory factor analysis extracted four common factors (maternal factor, infant factor, mother-infant dyad factor, and breastfeeding environment factor), with a cumulative variance contribution rate of 73.032%.Confirmatory factor analysis indicated that the four-factor model fitted well, with AVE values ranging from 0.557 to 0.658 and composite reliability ranging from 0.856 to 0.920.The square roots of the AVE for each factor (0.746 to 0.811) were greater than the correlations between that factor and the other factors.The overall Cronbach′s α coefficient for the scale was 0.925, and the Spearman-Brown split-half reliability was 0.820.The scale-level content validity index (S-CVI/Ave) was 0.960, while the item-level content validity index ranged from 0.880 to 1.000.Conclusion The Breastfeeding-related Stress Scale was constructed with good reliability and validity to assess the level of lactation stress in postpartum women.