Objective To investigate the effect of accuracy of phase 3 Oxford prosthesis positioning on short-term effectiveness of unicompartmental knee arthroplasty (UKA). Methods The clinical data of 26 patients (26 knees) who were treated with UKA between September 2015 and November 2015 was retrospectively analyzed. The single-peg Oxford prosthesis was implanted in 15 patients (single-peg group), and twin-peg Oxford prosthesis was implanted in 11 patients (twin-peg group). There was no significant difference in gender, age, body mass index, Kellgren-Lawrence grading, and preoperative Hospital for Special Surgery (HSS) scores between 2 groups (P>0.05). HSS, knee society score (KSS), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and Oxford knee score (OKS) were used to evaluate the knee function. Radiographic criteria for Oxford UKA was used to evaluate the prosthesis position. The reason and treatment of bearing dislocations were recorded. Results All patients were followed up with mean follow-up time of 26.2 months in single-peg group (range, 24-27 months) and 25.2 months in twin-peg group (range, 24-26 months). The bearing dislocation occurred in 2 cases of twin-peg group during follow-up. At last follow-up, there was no significant difference in HSS, WOMAC, OKS, and KSS scores between 2 groups (P>0.05). There was no significant difference in radiographic scores of femoral component, tibial component, and overall components between 2 groups (P>0.05). No significant correlation was found between radiographic scores and postoperative functional outcome in 2 groups (P>0.05). Conclusion Within a safe range, the accuracy of phase 3 Oxford prosthesis positioning has limited influence on the short-term functional outcome.