Abstract： Objective To investigate clinical value of pubococcygeal line (PCL) determined by dynamic magnetic resonance imaging (MRI) used in evaluating pelvic organ prolapse (POP), and investigate the relationship of pelvic organ prolapse quantitation (POP-Q) stage and pubococcygeal line (PCL) for the patient with POP. Methods Twenty patients with POP were evaluated by POP-Q stage and pelvic dynamic MRI examination simultaneously. Sagittal MRI images were acquired at rest and during maximal Valsalva using a fast gradient echo sequence two-dimensional fast low angle shot (FLASH) T1weighted image. The degree of prolapsed anterior vaginal wall, uterus and posterior vaginal wall were measured by PCL and compared with POP-Q system. Results There were 20 cases with cystocel diagnosed by POP-Q staging system, in which bladder neck or bladder base of 17 patients were under the PCL during maximum Valsalva. The concordance rate was 85% (17/20) between PCL and POP-Q stage. There were 19cases with rectocele diagnosed by POP-Q, in which the anorectal junction of 4 patients' PCL descent below more than 2. 5 cm. The concordance rate was 4/19 between PCL and POP-Q stage. There were 14 cases with uterine prolapse diagnosed by POP-Q staging system, in which uterine cervix of all descent below PCL. The concordance rate was 14/14 between PCL and POP-Q stage. However, it was noted that 5 cases did not reach POP-Q staging and their lowest uteri cervix were below or above PCL but less than 1 cm at maximal Valsalva. Conclusions Compared with POP-Q staging system, the reference line of PCL determined by dynamic MRI could diagnose uterine prolapse accurately and anterior vaginal wall with greater clinical value,however it was limited in diagnosing posterior vaginal wall prolapse effectively. Therefore, the clinical value of PCL should be further studied for evaluating POP.