Objective To investigate the clinical value of perineal fourdimensional ultrasound pelvic floor dynamic imaging in the grading and classification of primiparas pelvic floor dysfunction. Methods 92 patients with primiparas pelvic floor dysfunction (bladder prolapse) were selected. According to the general data and imaging data, the women were divided into vaginal delivery group (n=46) and cesarean section group (n=46). The images of bladder and urethra and pelvic diaphragm hiatus at rest, valsalva maneuver and anal status were observed. The bladder related parameter and Green typing were performed. Results The resting corresponding BSD and posterior horn of bladder and urethra of the two groups had no statistic difference (t=0.498, 0.370; P=0.619, 0.370). Under valsalva state, the corresponding to BSD, posterior horn of bladder, the bladder neck mobility and urethra and rotation angle of the cesarean section group were lower than those of the vaginal delivery group (t=2.016, 3.792, 3.036, 3.786, P＜0.05). According to the Green typing, the number of the type I, type Ⅱ and type Ⅲ in vaginal delivery group were 6 cases (13.04%), 26 cases (56.52%), and 14 cases (30.43%), which were significantly lower than 14 cases (30.43%), 23 cases (50.00%), and 9 cases (19.56%) in the cesarean section group, with statistic difference in the percentages between groups (x2=4.089, P=0.043), while no difference was found in the cystocele cases between the groups (x2=0.393, 3.737; P＞0.05). Conclusion The perineal fourdimensional ultrasound pelvic floor dynamic imaging can clearly demonstrate the pelvic floor anatomy, which can effectively distinguish the pelvic floor Green type and provide reliable imaging data for primiparas pelvic floor dysfunction.