Abstract: Objective To investigate the effect of immunomodulator ribonucleic acid Ⅱ on anastrozole-related joint symptoms. Methods A total of 156 postmenopausal women patients with stage Ⅰ-Ⅲ breast cancer and anastrozole-related joint symptoms were enrolled. These patients were divided into two groups： One group were treated by ribonucleic acid Ⅱ（200 mg， intravenous infusion， 1 time a day）as the experimental group， the other was treated by saline as the control group. The degree of symptom change was evaluated by FACT-G and WOMAC. The levels of serum cytokines（IFN-γ and IL-4）， the bone gla protein（BGP）， bone alkaline phosphatase（BALP） and I collagen carboxyl-terminal propeptide（CICP） of bone metabolism were detected by ELISA method. Results In comparison with the control group， ribonucleic acid Ⅱ significantly reduced the severity of musculoskeletal symptoms and pain， and also improved the quality of life（P＜0.05）. In ribonucleic acid Ⅱ group， the blood level of IL-4 was increased， whereas IFN-γ was decreased（P＜0.05）. as well as， the indexes of bone metabolism BALP and CICP were significantly lower than those in the control group（P＜0.05）. Conclusion Ribonucleic acid Ⅱ could improve aromatase inhibitor related musculoskeletal symptoms by the role of immunity adjustment.