Objective To explore the characteristics and significance of functional connectivity (FC) of affective network (AN) in patients with postpartum depression (PPD) under resting state. Methods A total of 23 patients with PPD (PPD group) and 28 healthy postpartum women (control group) were examined using resting-state fMRI. As two critical nodes of AN, amygdala (AMYG) and subgenual anterior cingulate cortex (sgACC) were selected as the regions of interest (ROI) to analyze the differences of functional connectivity strength (FCS) of two regions from other brain regions between two groups, followed by Pearson correlation analysis on the abnormal FCS and the Edinburgh postnatal depression scale (EPDS) score in PPD group. Results Compared to the control group, the patients in PPD group showed the extensively reduced FCS (P<0.05, Alphasim correction) between AMYG and frontal cortex, temporal cortex, hippocampus, cerebellum and orbitofrontal cortex, while there were enhanced FCS (P<0.05, Alphasim correction) between sgACC and parietal cortex, occipital cortex, thalamus, superior temporal gyrus and cingulate cortex. Moreover, in PPD group, the reduced FCS between left AMYG and left medial orbitofrontal cortex was negatively correlated with EPDS scores (r=-0.62, P=0.02). Conclusion Patients with PPD have dysfunctional connectivity of AN in multiple brain regions. The weaker FCS between left amygdala and left medial orbitofrontal cortex is, the more severe depression. The dysfunctional connectivity of AN may provide an effective mechanism-based biomarker underlying PPD.