Background: Breastfeeding knowledge, attitude, self-efficacy, and social support are affective of a mother’s confidence in breastfeeding which are influencing factors of breastfeeding ways. Knowledge, attitude, self-efficacy, and social support play important and positive role in promoting breastfeeding behavior in macrosomia.Methods: Collect breastfeeding knowledge, attitude, self-efficacy, and social support scale of 332 mothers of macrosomia, state the current breastfeeding condition macrosomia in China, investigate the influencing factors of breastfeeding way. Using t test for continuous variables and chi-squared or Fisher’s exact test for categorical variables.Results: The study collected Breastfeeding knowledge, attitude, self-efficacy, and social support scale of 332 mothers of macrosomia (148 from breastfeeding group and 184 from non-breastfeeding group). Compared with mothers in control groups, mothers in breastfeeding groups had significantly higher knowledge score, and most of the high-scoring items on the knowledge scale pertained to maternal breastfeeding benefits. Although the attitude had no significant difference between the two groups, most majority of participants (71.4% and 73.2%, respectively) perceived breastfeeding could increase the intimacy of mother and infant (95.41% and 94.75%, respectively). Breastfeeding ways were great influence by self-efficacy. Over half of participants (55.41% and 53.26%, respectively) stated that they “have more than 3 friends who can get support and help,” although up to 95% in both groups supported from family members.Conclusion: This study state that knowledge, attitude, self-efficacy and social support are influencing factor that to improve breastfeeding rates of macrosomia, which promote the breastfeeding outcomes.