OBJECTIVE To analyze the reasons of early failure of the PHILOS in proximal humerus fractures. METHODS From Nov. 2010 to Nov. 2014, there were 117 patients with humerus fractures treated with PHILOS locking plate in Department of Orthopaedics, Xuanwu Hospital. All of the patients were treated with the plate by open reduction internal fixation, and we analyzed these cases retrospectively. After the operation, we removed the drainage tube within 48 h, and the patients were allowed to do the passive motion 3 days after the surgery if the X-Ray showed the plate and screws were reliable. Eight cases failed within 4 weeks after the operation. We analyzed the reasons of the failure. RESULTS The rate of the failed cases was 6.83%(8/117). The average age was 72.4(66-82) years. In the 8 failed cases, 3 were on the right side, and the other 5 on the left side. As for the reason of the fractures, 2 cases were because of car accidents, and the other 6 because of daily life injury. According to the Neer classification, 3 cases were 2-part fractures, and the other 5 3-part fractures. Three cases were total failure, and the other 5 partial failure. All the 8 failed cases failed within 4 weeks after the operation, of which 1 was on the sixth day after surgery, the other 7 2 to 4 weeks after the surgery.The 3 totally failed cases were treated by removing the screws and plates, the other 5 by conservative methods. All of the cases were malunion at the end. CONCLUSION The early failure of the PHILOS locking plate in proximal humerus fractures is related to the bad reduction during the operation, the loss of medial cortex support, the limitation of screw length, the osteoporosis and the improper rehabilitation after operation.It is very important to do good preoperative plan for a surgeon. During the operation, we should try our best in the fracture reduction, use the appropriate plate and screws, and then pay attention to the rehabilitation after the operation. After all of this, the rate of failure may be decreased.