Background Genital prolapse affects 30% of middle-aged and older women and is becoming a major public health concern. Sacrospinous ligament fixation is an effective and safe procedure for vaginal vault prolaps with a low recurrence and complication rate. This study aimed to investigate the efficacy and safety of unilateral sacrospinous ligament fixation (SSLF) for the management of pelvic organ prolapse (POP).Methods Forty patients with severe prolapse of pelvic organ undergoing unilateral SSLF were retrospectively studied.In this study, all patients were staged by the value of POP-Q. All procedures were performed by a senior physician. The characteristics of these patients and their immediate and short-term post-operative outcome were recorded. All patients were seen six weeks and six months after the surgery. The evaluation included standardized questionnaire and site-specific vaginal examination by one physician.Results The average operation time was 65-92 minutes. The average blood loss was 83-188 ml. The average hospitalization time was 6.1 days. The average cost was 5885 yuan. The average day of urethral catheter removal after the operation was 2.1 days. The incidence of postoperative morbidity was 17.1%. One (2.4%) patient had hematoma in the right pelvic. The mean length of postoperative follow-up for 35 patients was 13.1 months. The rate of follow-up was 87.5%. One (2.9%) patient showed recurrent vaginal vault prolapse six months after the surgery. The objective success rate of pelvic organ prolapse was 85% (34/40). There was significant difference between the POP-Q of Aa, Ba, Ap, Bp,and D before and after operation (P ＜0.001 ). Five (14.3%) patients complained lower back pain, gluteal pain or right groin pain. Three (8.6%) patients developed de novo stress incontinence. Vaginal disabsorbable sutures were found in three (8.6%) patients. One (2.9%) patient had de novo urge incontinence.Conclusions Unilateral SSLF was both cost and treatment effective management for severe pelvic organ prolapse,especially for severe ovaginae anterior prolapse and uterus prolapse of POP Ⅰ, Ⅱ or Ⅲ. Main complications from this procedure included lower back pain, gluteal and groin pain and new onset of stress incontinence.