OBJECTIVE To study the clinical effects and security of nanometer ceramics artificial bone transplantation to treat the bone defect. METHODS From March 2005 to November 2007, 32 patients (artificial bone group) with extremity bone defects applied nanometer ceramics artificial bone transplantations, included 19 males and 13 females, aged from 17 to 63 years old (averaged 31.4 years). The other 36 patients (internal fixation group) with extremity bone defects were treated by the internal fixation in the same period, included 21 males and 15 females, aged from 16 to 65 years old (averaged 32.6 years). Ca, P, B-ALP, IgG, IgA, IgM, CIC, C3, SL-2R and CD4+/CD8+ in the peripheral venous blood were measured in the 1st and 2th week and 1st, 3rd, 6th month after operation. All patients were followed up and the limb function was evaluated according to Enneking standard. RESULTS The wounds of all patients smoothly healed after operation. Every immunological indicators had no significant difference between two groups. Serum calcium and phosphorus content did not significantly increased. Serum B-ALP of all patients were increased after operation, fell to normal levels in the internal fixation group, but remained at a relatively high level in the artificial bone group. All patients were followed-up for from 9 to 24 months (averaged 15 months). All patients get the excellent physical function. CONCLUSIONS The artificial bone has no immunogenicity, no rejection,does not affect the blood calcium and phosphorus content, and has higher osteogenic activity. It is affirmed that nanometer ceramics artificial bone is used to treat the smaller bone defect on clinical.