Objective To investigate the clinical effect of threedimensional (3D) printingguided unicompartmental knee arthroplasty (UKA), and provide a basis for individualized and accurateartificial UKA.Methods From August 2017 to January 2019, 80 patients with medial compartment arthritis of knee joint were randomly divided into 3D printing individualized guide group (PSI group, n=40) and traditional UKA group (CON group, n=40). In the PSI group, the age of the patients ranged from 50 to 68 years (58.5%±11.5 ). In con group, the age of patients ranged from 55 to 72 years (61.5%±23.6). The operation time, blood loss, postoperative ambulation time, hospital stay, ROM, VAS, HSS and HKA were compared between the two groups.Results The operation time in the traditional UKA group and PSI group were (69.5±8.8) min, (56.3±4.9) min. The length of hospital stay in the traditional UKA group and PSI group were 6.8±2.1 d and 5.0±1.5 d (P＜0.05). The intraoperative blood loss in the traditional UKA group and PSI group were 50.6±5.5 mL and 48.5±4.0 mL (P＞0.05). The landing time after operation in the traditional UKA group and PSI group were 6/4±2.5 and 5.5±4.0 h (P＞0.05). The VAS score, KSS score, and knee joint mobility (ROM) of all patients were significantly improved compared with those before surgery, with significant differences and statistical significance.There was no significant difference in VAS score, HSS score and ROM at 3 months after operation (P＞0.05). The HKA angle of the PSI group at 3 months after operation was (178°±2.3°), CON group was(176°±2.3°). There were statistical differences between two groups in these two items(P＜0.05).Conclusion The effect of 3D printing PSI guided osteotomy is highly consistent with the preoperative plan, and the osteotomy angle and prosthesis position are more accurate, which can reduce the operation time and hospital stay, and obtain better shortterm clinical efficacy.