Abstract:[Objective] To introduce the surgical technique and preliminary clinical outcomes of unicondylar knee arthroplasty (UKA) with tibial precise osteotomy by the mechanical arm guided by celestial eye computer surgery system. [Methods] A total of 20 patients with medial-compartment osteoarthritis of the knee received the abovesaid surgery. The CT data of patients were collected before operation, and then imported into the celestial eye system to select appropriate prosthesis and plan the position of prosthesis. During the operation, a com- puter guided mechanical arm was used to insert 3 Kirschner wires into the proximal tibia, perform precise osteotomy along the direction of the Kirschner wires, place matching tibial component to finish the computer guided UKA surgery. The postoperative knee function and imag- ing data were followed up 6 months after operation to evaluate the surgical outcomes. [Results] All 20 patients were successfully operated on, with operation time of (48.5±8.6) min and blood loss of (47.5±10.1) ml, whereas without serious complications. Compared with those preoper- atively, 6 months after operation the knee range of motion (ROM) [(88.9±12.3)° vs (102.8±8.4)°, P＜0.05], KSS clinical score [(51.4±10.3) vs (89.7±3.0), P＜0.05] and KSS functional scores [(41.7±14.4) vs (83.3±6.9), P＜0.05] significantly improved. In addition, the posterior tibial slope, varus and varus, internal and external rotation angles of tibial component placed, as well as the tibial osteotomy thickness proved high- ly consistent with those of preoperative planning (P＞0.05). [Conclusion] The UKA with tibial precise osteotomy by the mechanical arm guid- ed by celestial eye computer surgery system is considerably effective and convenient, with shortening learning curve of this procedure.