Abstract: Objective To explore the effect of aromatase inhibitors-anastrozole on IL-17 and RANKL/RANK/OPG in the serum of collagen induced arthritis(CIA)rats and to illustrate its aggravation on bone.Methods CIA rats were divided randomly into 3 groups:anastrozole group(A),ovarectomy group(O)and sham operation group(S).The edema rate of ankle joints were examined.The radiological injuries of ankle were observed by molybdenum target radiography.The production of IL-17 and RANKL/RANK/OPG in the serum were determined by enzyme linked immunosorbent assay(ELISA).Results Compared to ovarectomy group,administration of anastrozole significantly increased the severity of arthritis(P＜0.05),the levels of IL-17 and RANKL in anastrozole group were significantly higher,whereas,OPG expression was lower.Moreover,the ratio of RANKL/OPG obviously increased(P＜0.05).Conclusion Anastrozole potently promots the progression of CIA model by the increasing of IL-17、RANKL and decreasing of OPG.