Objective To compare the associations between different modes of delivery and the pelvic floor function of primiparous women at early postpartum through pelvic floor muscle surface electromyography（sEMG）. Design Retrospective observational study. Population A total of 3638 primiparas who experienced singleton delivery were selected as the research objects. Methods There were 1469 cases of cesarean section delivery (CD) and 2169 cases of vaginal delivery (VD). Furthermore, the vaginal delivery group were separated into four subgroups. The pelvic floor sEMG indexes of the subjects were analyzed at 6–8 weeks postpartum. Main outcome measures The pelvic floor sEMG were compared between CD and VD，and the four vaginal delivery subgroups. A modified Glazer protocol was used to analyze the pelvic floor sEMG value. Results The results showed that the average peak amplitude of phasic (flick) contractions and the average mean amplitude of tonic contractions were both significantly higher in CD than in VD (P < 0.01). In contrast, CD had less the mean amplitude variability of tonic contractions than VD (P < 0.01). The average peak amplitude of phasic (flick) contractions and the average mean amplitude of tonic contractions in forceps delivery group was statistically lower than the other vaginal delivery groups (P<0.05). The mean amplitude variability of tonic contractions was larger in forceps delivery group than group A, B. (P <0.01). Conclusion There is a clear link between mode of delivery and pelvic floor sEMG at 6-8 weeks postpartum in primiparas. Keywords pelvic floor dysfunction；pelvic floor muscle surface electromyography；postpartum；delivery mode；Glazer protocol