The objective was to evaluate the efficacy of pessaries in the treatment of stage IV pelvic organ prolapse (POP) and identify the influencing factors.One hundred and fifty-seven patients with stage IV symptomatic POP were admitted to the hospital for pessary fitting. A successful pessary fitting was defined as a patient fitted with a pessary at the initial fitting in whom use continued 2 weeks later. The rates of successful pessary fitting, patient satisfaction, remission of prolapse and urinary symptoms, and the occurrence of factors associated with successful pessary fitting were calculated and predictors of appropriate pessary type selection were analyzed.A total of 130 patients with stage IV POP had a successful pessary fitting (82.8%). The satisfaction rate associated with the two types of pessaries was more than 90%. The success rate among patients undergoing a ring pessary fitting trial was 44.6%, and 84.3% of the patients were self-managed. Prolapse symptoms significantly improved in 90% of cases, and urinary symptoms improved in 58-93% of cases from baseline. The number of vaginal deliveries, history of hysterectomy and vaginal introitus/total vaginal length (TVL) ratio were independent risk factors associated with unsuccessful pessary fitting.For patients with stage IV POP, the successful fitting rate is as high as 80% or more. More vaginal deliveries, a history of hysterectomy, and a larger vaginal introitus/TVL ratio (ratio  >0.6) were predictors of unsuccessful pessary fitting.