Abstract: Objective To explore the clinical effect of X-N advancement flap in repairing pressure ulcer on the buttock or back. Methods From June 2018 to June 2019, 20 patients with grade Ⅳ pressure ulcers on the buttock or back were hospitalized and treated in the Department of Traumatology, Burns and Plastic Surgery of Fourth Affiliated Hospital of Guangxi Medical University, including 15 males and 5 females, aged 48-89 years. The area of the patient′s wound was 8 cm×5 cm-15 cm×12 cm after debridement, and all were repaired with the X-N advancement flap designed by the author. The flap was designed according to the direction of skin relaxation on both sides of the wound, and the skin was incised in X-shape and sutured in N-shape. The width and advancement distance of the flap were recorded, and the ratio of the advancement distance to the width of the flap was calculated. The flap survival, complication, and follow-up were observed and recorded. Results The width of the flap was (5.9±1.2) cm, the advancement distance of the flap was (10.3±2.5) cm, and the ratio of the advancement distance to the width of the flap was 1.8±0.4. All the flaps survived, and none of the flaps had blood flow disorder. Local dehiscence occurred in the flap of one patient 1 week after surgery, which was healed after laying on the floating bed, strengthened care, and wound dressing change. The flap of one patient developed infection 5 days after surgery, which was healed after partial suture removal, smooth drainage, and replacement with sensitive antibiotics. The wounds of the remaining 18 patients were all cured. After 3 months of follow-up, the flaps survived well with good elasticity and texture. Conclusions The X-N advancement flap can make the skin and soft tissue move forward effectively. It is simple and effective to repair pressure ulcers on the back or buttock of patients with this flap, which is worthy of clinical promotion and application.