Background: To investigate the effect of different delivery modes and related obstetric factors on the short-term strength of the pelvic floor muscle after delivery in Chinese primipara. Methods: A total of 4769 healthy Chinese primiparas at postpartum 6-8 weeks were interviewed. According to the difference of delivery mode, the selected primiparas were divided into 2 groups, including cesarean delivery group containing 2020 and vaginal delivery group containing 2749. All the vaginal deliveries were further divided into 3 groups, including episiotomy group containing 2279, perineal laceration group containing 398, and forceps assisted group containing 72. The scales of their pelvic floor muscle (PFM) strengths were examined by specially trained personnel using digital palpation (Modified Oxford scale:0-5 grade). According to participants' willingness, if the PFM strength was weak (0 or 1 grade), at-home PFM training would be recommended and an electrical stimulation combined with biofeedback therapy would be conducted for them in hospital. Twelve weeks after delivery, the PFM strength would be measured again. For statistical analysis, t-test, one-way variance analysis, Chi-square analysis, Kruskal-Wallis test H, Mann-Whitney U test and Wilcoxon test were carried out. Results: The PFM strength in cesarean delivery group was higher than in vaginal delivery group (p < 0.05). Among 3 vaginal delivery groups, the PFM strength in perineal laceration group was the highest (p < 0.05); however, there was no difference in PFM strength between episiotomy group and forceps assisted group (p>0.05). After accepting PFM training at home and therapy in hospital, 305 women showed increased PFM strength (p < 0.05). Conclusions: Vaginal delivery is an independent risk factor causing the damage of PFM, and episiotomy may cause injury of PFM. Through PFM training at home and therapy in hospital, those damage will resume as soon as possible in the short-time period after delivery.