Objective:To investigate the clinical efficacy of posterolateral locking plate in the treatment of large posterior malle-olar fracture .Methods :From January 2010 to June 2012 ,23 patients with large posterior malleolar fractures were treated by posterolateral locking plate ,including 15 males and 8 females ,all of whom aged from 32 to 78 years with an average age of 43 .7 years .The average time from injury to operation was 7 .3 days ,which ranged from 5 to 12 days .Calcaneal traction fixa-tion or plaster was performed on the injured limb before operation .Once that swelling reduced ,all patients were treated by posterolateral locking plate and were assessed with the ankle hindfoot clinical rating system of the American Orthopaedic Foot and Ankle Society (AOFAS) .Results:The follow-up time was from 14 to 22 months ,with an average period of 17 .4 months . 23 patients resulted in bone healing ,without loosen or breakage of internal fixation .As the X-ray pictures showed ,fracture healing time after operation ranged from 11 to 21 weeks ,which was 14 .7 weeks on average ,and full weight bearing time was from 15 to 25 weeks ,which was 17 .1 weeks on average .The AOFAS scores ranged from 73 to 94 points with an average of 83 .4 points at the 12th month after operation .One patient had superficial wound infection at the 7th day after operation and was healed by sensitive antibiotics and changing fresh dressing .Conclusions :Posterolateral locking plate could be a good method for the treatment of posterior malleolar fracture because effective redution and proper fixation could be obtained through straight access .