Abstract: Research results about the negative effects of postpartum depression(PPD) on breast feeding tend to be consistent, while it is not clearly that whether breastfeeding can reduce the incidence of PPD. Considering the importance of maternal mental health and the breastfeeding to infant' health, it is worth exploring the interaction and causality between PPD and breastfeeding, so as to provide high-quality evidence for medical staff to carry out the interventions.