Abstract: Objective：To analyze the changes of maternal pelvic muscle strength after vaginal delivery and to explore the risk factors for pelvic muscle damage. Methods：Totally 288 postpartum women, who all vaginally delivered in Obstetrics and Gynecology Hospital of Fudan University, were enrolled in the study between April and June in 2015. Their pelvic floor screening results were retrospectively summarized. Their clinical data were obtained by retrieving their medical, and then the potential influencing factors of postpartum pelvic muscle damage were analyzed via Logistic regression analysis. Results：Among 288 postpartum women, 252 cases (87.5%) encountered postpartum pelvic muscle damage. 149 cases (51.7%) were diagnosed with anterior vaginal wall prolapse, 29 cases (10.1%) with posterior vaginal wall prolapse, and 7 cases (2.4%) with uterine prolapse. Logistic univariate analysis and multivariate analysis both showed that only newborn birth weight was associated with pelvic muscle damage (P＜0.05), but other obstetric factors such as maternal age, parity, gestational age, body mass index, forceps delivery, the time of first/second stage of labor and episiotomy were not associated with pelvic muscle damage. Conclusions：Pregnancy and childbirth are important factors leading to pelvic muscle abnormalities and pelvic organ prolapse. Pelvic muscle damage were significantly correlated with newborn birth weight.