This paper proposes a semi-autonomous robot control system for mandible reconstruction surgery. To reconstruct a segmental defect of the mandible caused by cancerous tissue, a piece of matched fibula bone is often segmented and used to replace the removed mandible section. In this paper, to provide guidance to the surgeon during fibula segmentation according to the reconstruction surgical plan and to improve the fibula bone cutting accuracy, an admittance-controlled robotic assistant incorporating 3D augmented reality (AR) visualization and haptic virtual fixtures (VF) is proposed. The admittance controller is used to reduce the surgeon’s hand tremor. The VF and AR are used to provide haptic and visual guidance to the surgeon, respectively. A feasibility study is performed through a comparison of fibula osteotomies when performed with image-guided surgery, AR-guided surgery, VF-guided robot-assisted surgery, and AR-and VF-guided robot-assisted surgery. Experimental results show the effectiveness of the proposed admittance-controlled robotic assistant with AR and VF compared to the other three methods. The proposed method was found to beable to increase precision of the osteotomized segments with a lower average linear variation of 1.04 ±0.79 mm and a lower average angular variation of 1.83 ±1.85° compared to the virtual preoperative plan.