Abstract: Objective To evaluate the effect of vaginal delivery and selective caesarean section on female area of delphragma pelvic hiatus by real-time three-dimensional ultrasound.Methods 303 women who underwent the transperineal real-time three-dimensional ultrasound in 6-8 weeks after childbirth from January 2016-2017 June in Women And Children's Health of Hunan Province were divided as the vaginal delivery group and the cesarean section group. The area of delphragma pelvic hiatus in the resting stage, anal sphincter contracting stage and maximum Valsalva condition was observed and measured.Results There was significant statistical difference inthe delphragma pelvic hiatus areas in maximum Valsalva condition between the two groups (P<0. 01). There was statistical difference in the delphragma pelvic hiatus area in the resting stage between the two groups (P<0. 05). However, there was no difference the delphragma pelvic hiatus area in the anal sphincter contracting stage.Conclusion Compare with selective caesarean section, there are more short term influences at the area of delphragma pelvic hiatus by vaginal delivery. According to observe the variation of the delphragma pelvic hiatus area in the resting stage and maximum Valsalva condition by transperineal realtime three-dimensional ultrasound, the effects to the pelvic floor for pregnancy and different delivery methods can be evaluated.