Objective: To evaluate the clinical efficacy of total arthroscopic anterior talofibular ligament repair for chron-ic lateral instability of ankle joint. Methods: Data of 70 patients with chronic lateral mechanical instability of ankle joint treated by anterior talofibular ligament repair under full scope from September 2016 to October 2017 were retrospectively analyzed. There were 48 males and 22 females, aging from 18 to 49 years old (average, 32.3±3.4 years). Arthroscopic exploration, synovial mem-brane cleaning, extraction of lateral malleolus free body or microfracture were used in the operation, and the anterior talofibular lig-ament was repaired with knottless anchors to restore ankle stability. After the operation, plaster support was used for fixation, and relevant rehabilitation plans were conducted. X-ray films of the front drawer stress position of the ankle joint was taken preopera-tively and during follow-up, and the talus advancing distance was measured preoperatively and during follow-up. Ankle function was evaluated by American Orthopaedic Foot and Ankle Society (AOFAS) ankle and hindfoot function score, and pain was evaluat-ed by visual analogue scale (VAS). Results: Seventy patients were followed up for 8-18 months, with an average of 11.5 months. The incisions of all patients were healed in one stage without internal plant rejection reaction. The plaster was fixed for 2 weeks af-ter operation, followed by rehabilitation training 2 weeks later, non-confrontational physical exercise 3 months later and confronta-tional physical exercise 6 months later. Within one year after operation, 58 patients could meet the needs of daily life and exercise. Seven basketball and football fans complained of ankle joint soreness and discomfort after strenuous exercise, and the symptoms were relieved after treatment. The symptoms of foot and ankle instability were not significantly improved in 5 patients. Stress X-ray showed that the talus advancing distance was improved from 11.70±1.05 mm before operation to 3.25±1.09 mm at the latest follow-up, and the difference was statistically significant (t=32.15, P< 0.0001). VAS decreased from 5.70±2.90 before operation to 2.05±0.52 at the latest follow-up (t=11.75, P< 0.0001). AOFAS increased from 54.50±7.40 before operation to 87.80±5.60 at the latest follow-up (t=34.04, P< 0.0001). There was excellent in 53 cases, good in 8 cases, fair in 5 cases, poor in 4 cases, thus the excellent and good rate was 87.14% (61/70). One of the patients suffered from joint pain in ankle metatarsal flexion half a year later, and MRI reexamination found that the anchor had entered the joint cavity, whose symptom was relieved after the anchor was cleared by arthroscopy at the later stage. Conclusion The treatment of lateral chronic instability of ankle joint with arthroscopic non-knot anchor nail repair of anterior talofibular ligament can effectively restore the stability of ankle joint and the movement ability of pa-tients. The operation has advantages of definite curative effect, minimally invasive, fast recovery and easy acceptance by patients.