Objective To investigate the factors affecting the structure of postpartum pelvic floor by three-dimensional ultrasound and to provide evidence for the prevention of postpartum pelvic organ prolapse (POP). Methods A total of 138 women giving birth in our hospital from January 2016 to October 2017 were selected. Three-dimensional ultrasound examination was performed on the subjects. The resting urethral tilt angle, Valsalva bladder neck position, Valsalva were continuously observed. The correlation between different POP ultrasound parameters and clinical indicators were analyzed. Results The maternal pregnancy, age and infant weight had little effect on POP (P > 0.05). The distance of valvular vaginal to reference line and bladder posterior urethral angle were statistically significant among the subjects with different production times (P <0.05). The more births, the higher the incidence of Valsalva cervix to the reference line >15mm and the bigger the posterior angle of the bladder urethra (degree); the resting urethral tilt angle, the position of Valsalva bladder neck, the distance of Valsalva cervix to reference line and the distance of Valsalva rectal ampulla to the reference line were statistically significant among pregnant women with different body mass index (BMI) (P<0.05); the urethral tilt angle and the abnormal rate of bladder urethral angle of the pregnant women with BMI ≥25 kg/m2 were significantly higher than those of pregnant women with BMI <25 kg/m2 (P<0.05). Conclusions Prolific secondary and high BMI are related factors affecting pelvic floor organ prolapse. The pelvic floor ultrasound can dynamically monitor and intervene in the occurrence of pelvic floor organ prolapse.