Objective To summarize the effectiveness of 3.5 mm T support plate fixation for simple postero-lateral tibial plateau fractures by posterolateral inverted L-shaped approach. Methods Between March 2011 and January 2016, 13 patients with simple posterolateral tibial plateau fracture were treated with 3.5 mm T support plate fixation by posterolateral inverted L-shaped approach. Of 13 cases, 6 were male and 7 were female, aged 28 to 52 years (mean, 43 years). The left side was involved in 5 cases and the right side in 8 cases. The causes of injury were traffic accidents in 6 cases, falls in 3 cases, and falling from height in 4 cases. All of patients had fresh closed fracture by X-ray, CT three dimensional reconstruction, and MRI. According to Schatzker classification, 4 cases were rated as type II and 9 cases as type III. The time between injury and operation was 5-9 days (mean, 7 days). Results One case had incision skin necrosis, which was cured after debridement and skin grafting; and primary healing was obtained in the other cases. The patients were followed up 10-16 months (mean, 13 months). The X-ray film showed that the fracture line was blurred at 3 months after operation, and disappeared at 12 months after operation. There was no complications of wound infection, major neurovascular injury, loosening or breakage of internal fixation, and dislocation of joint surface. The Hospital for Special Surgery (HSS) knee function score was 94 (range, 89-97) at last follow-up; all were excellent. Conclusion The 3.5 mm T support plate fixation by posterolateral inverted L-shaped approach is one of preferred surgical method for the treatment of simple posterolateral tibial plateau fractures.