Abstract:[Objective] To introduce the preoperative design, surgical technique and clinical application effect of oblique single-cut rotation osteotomy corrects polyplanar deformity of femur. [Methods] One patient with malunion of femoral fracture was preoperatively designed, the osteotomy angle and rotation angle were determined, the operation was simulated on Mimics software, and the osteotomy guide plate was made by 3D printing. The case was treated with oblique single-cut rotation osteotomy. A longitudinal incision was made on the laterlal side of the femur to expose the malunion, an osteotomy guide was placed, and the osteotomy and rotation were completed according to the preoperative design. The fractured end of the osteotomy was fixed with intramedullary nails, and taken from the iliac bone for bone grafting. [Results] The operation was safe and there were no adverse complications after operation. After 6 months of follow-up, the patient was no longer limping, and no pain in the knee joint. CT confirmed that the fractured bone was completely healed. [Conclusion] The oblique single-cut rotation osteotomy is feasible, that can osteotomy, correct the coronal, sagittal and rotational deformities of the femur at the same time. A satisfactory clinical effect can be achieved in the short term.