Objective To determine the morphological changes of pelvic floor in the postpartum women with various delivery modes by transperineal 4D ultrasound. Methods 60 cases of natural labor group, 50 cases of cesarean section, and 50 cases of no pregnancy control group with normal pelvic floor structures were examined between May 2016 and October 2016. Data were collect at the 42nd day of postpartum, and pelvic floor ultrasonography were performed to record the shape and activity of bladder neck, cervix, rectum and anal canal in resting, contraction and Valsalva movements. Four-dimensional images were reconstructed to observe the shape and continuity of the pelvic diaphragm hiatus in the three temporal states. The area of the pelvic diaphragm hiatus was measured, and the results were recorded and compared. Results The area of the pelvic diaphragm hiatus was 16.29 ± 3.28cm2 in the control group, 18.6 ± 3.54cm2 in the natural labor group and 16.52 ± 2.74 cm2 in the cesarean section group respectively at rest. With pelvic floor contraction, this area change to 10.45 ± 4.12 cm2 in the control group, 15.18 ± 3.07 cm2 in the natural labor group and 12.83 ± 2.51 cm2 in the cesarean section group. In Valsalva, the area of pelvic diaphragm hiatus was 14.32 ± 4.44 cm2 in the control group, 22.15 ± 6.10 cm2 in the natural labor group and 19.66 ± 3.68 cm2 in the cesarean section group, respectively. The activities of bladder neck were 13.17 ± 5.64mm in the control group, 23.63 ± 6.35mm in the natural labor group and 17.00 ± 6.52mm in the cesarean section group. Uterine prolapse, control group 0 cases, natural childbirth group 9 cases (15%), cesarean section 0 cases. Rectal prolapse was only found 1 cases (1.67%) in natural childbirth group. The crack area and bladder neck activity under resting state, pelvic floor contraction state and Valsalva action were natural childbirth> cesarean section> control group. Uterine prolapse and the incidence of rectal prolapse were spontaneous delivery> cesarean section group> control group. Conclusion Natural childbirth has more influence on pelvic floor than cesarean section. Transperineal four-dimensional ultrasound can evaluate the different modes of delivery on the pelvic floor structures.