【Abstract】 Objective To observe the effect of different delivery methods on the pelvic cavity of the first female with pelvic floor ultrasonography.Methods 68 patients of primipara were analyzed. According to the different modes of delivery, the patients were divided into observation group (vaginal delivery) and control group (cesarean delivery). The morphology and characteristics of pelvic diaphragm hiatus hole and the related parameters and BND were observed.Results The difference of the anteroposterior diameter, BND, circumference and area index between the left and right sides of the pelvic fissure in the different mode of delivery between the groups were obviously different (P＜005). There was significant difference between the two groups in the function of pelvic diaphragm hiatus in resting state, and the difference was statistically significant (P＜005).Conclusion The pelvic floor threedimensional ultrasound is convenient, fast, reproducible, cost-effective, and easy to accept. It is accurate, intuitionistic and clear for the phrenic hole of the pelvis, which provides an important role in the diagnosis of dysfunction.