Objective: To explore the application value of pelvic floor ultrasound in the changes of pelvic floor structure and pelvic dysfunction in pregnant women. Methods: 167 pregnant women who were singleton pregnancy and spontaneous delivery received dynamic examination of pelvic floor ultrasound for the measurement of the mobility of bladder neck (BND), the mobility of external cervix (CD), posterior horn of bladder (RVA), area of diaphragmatic hiatus (LHA), anteroposterior diameter (LR), transverse diameter (HA) during early pregnancy, second pregnancy, late pregnancy, delivery and postpartum. The characteristics of labor and the abnormal types of postpartum pelvic floor structure were analyzed. The incidence of pelvic floor dysfunction diseases and the efficacy of pelvic floor rehabilitation were compared. Results: The pelvic floor ultrasound indexes BND, CD, RVA, LHA, LR and HA gradually increased with gestational age. The difference between control group and observation group was found in the third trimester (P < 0.05).Within the observation group, there was a statistical difference between the third trimester, intrapartum(the maximum), the postpartum period and the first trimester (P < 0.05), but there was no statistical difference between the first and second trimester indicators (P>0.05).Postpartum and control group had statistical significance (P< 0.05).Long labor and mechanical assisted labor were correlated with abnormal structure of postpartum pelvic floor. The incidence of pelvic floor dysfunction diseases in women who participated in pelvic floor function rehabilitation was significantly lower than that of non-participants, and the difference was statistically significant (P < 0.05). Conclusion: Both pregnancy and vaginal delivery have a serious impact on female pelvic floor function and increase the risk of pelvic floor dysfunction. Pelvic floor ultrasound can clearly and intuitively reflect the pelvic floor structure of women during pregnancy and after delivery, and is noninvasive. Outstanding advantages such as nonradiative and repeatability have important clinical significance for preventing and diagnosing the occurrence of pelvic floor dysfunction diseases in pregnant women and postpartum women.