Since the implementation of “two-child policy” in China, the prevalence and influencing factors of postpartum depression (PPD) between women at first childbirth and second childbirth remains unclear. We aimed to compare the prevalence and the influencing factors of PPD between the two groups. Postpartum women were recruited at their 6-week postpartum checkups and invited to complete questionnaires. The prevalence rate of PPD was 42.1%. There was no statistical difference found regarding the prevalence of PPD and the total score on the Edinburgh Postnatal Depression Scale between the two groups. The median of the item “self-injury” was significantly higher among women at first childbirth. Women with gestational diabetes in pregnancy, antenatal anxiety and depression, abortion, having babies getting sick occasionally, and deteriorated relationships with partner in pregnancy had much higher risks for PPD. Both primiparous and secundiparous had a high prevalence of PPD. It provides scientific evidence for clinical preventive and nursing care for PPD.