Objective To compare the biomechanical characteristics of proximal tibia after unicompartmental knee arthroplasty (UKA) between conventional osteotomy, radial-corner shape reserved osteotomy and radial-corner shape extended osteotomy. Methods On the basis of CT data from the Sawbones tibia, the complete tibia model and the UKA model under different osteotomy methods were constructed. The finite element analysis was performed on these models under axial compression condition to compare the strain situation of proximal tibia and the difference of bone cement stress. Results Under axial compression conditions, the peak von Mises strain on the resected area of cortical bone was calculated. The strain of the radial-corner shape extended group was increased compared with that in regular osteotomy group and the radial-corner shape reserved group, while the peak von Mises strain of cancellous bone was decreased by 24. 3% -42. 9% and 26. 0% -48. 7% , respectively. Comparing the peak von Mises strain difference between cancellous bone and cortical bone in the resected area, it was found that the difference of the radial-corner shape extended group was much smaller than the other two groups. There were no significant differences in the minimum principal strain on the anteromedial tibial cortex between different models after UKA, but they increased by 23. 3% -34. 5% compared with the intact tibial model. The average von Mises stress in the cement unit of the radial-corner shape extended group tended to decrease as the fillet radius of the corner increased, which was smaller than that of the regular osteotomy group and the radialcorner shape reserved group. Conclusions The new radial-corner shape extended osteotomy method results in more uniform stress transfer to the proximal tibia under healthy bone conditions, lower peak von Mises strain, and less compression at the prosthesis-bone interface, which is more advantageous than regular osteotomy method and radial-corner shape reserved osteotomy method.