Abstract： Objective To explore the relationship of serum anti-MICA antibody and development of chronic rejection (CR) after renal transplantation. Methods The enrolled 105 patients included 43 cases of CR, and 62 cases of functioning renal allograft as controls. Data including PRA level before transplantation, HLA mismatch, cold ischemic time, SCr at discharge, immunosuppressive regimen,and months after transplantation were analyzed. Blood samples were collected immediately after grouping for anti-MICA antibodies, SCr determination. Acute rejection episodes and renal allograft function which was evaluated by △SCr/M [(SCr at present - SCr at discharge) /months after transplantation) were compared between anti-MICA-antibody positive patients and anti-MICA-antibody negative patients. Results There was no significant difference in gender, age, HLA mismatch, cold ischemic time, immunosuppressive regimen, SCr at discharge, months after transplantation between CR and control groups (P＞0.05). Serum creatinine level and number of antiMICA-antibody positive patients in CR group were significantly increased as compared with those in control group (P＜0.01 ). Acute rejection episodes during the first 3 months after transplantation in anti-MICA-antibody positive patients were significantly more than those in anti-MICA-antibody negative patients (P＜0.05),and the △SCr/M in the former was higher than that in the latter (8.3 +3.6 vs 2.4 ± 2.6, P＜0.05). Conclusion Humoral immunoreaction mediated by MICA partly participates the development of CR after renal transplantation. MICA antibody is a risk factor affecting long-term allograft function.