To observe the therapeutic effects of the nosocomial preparation namely Yajiakang capsules treating patients with subacute thyroiditis in acute stage(heat-toxin congestion and excessiveness type)and its influence on oxidative stress status.Methods：Divided 68 cases of patients in accordance with the inclusion criteria into two groups randomly，34 cases in each group.The treatment group was given Yajiakang capsules for treatment，while the control group was given prednisone for treatment.Both groups were treated for 2 months，detected the biochemical indexes before and after treatment，and statistically analyzed Chinese medicine syndrome scores.Results：Both groups could effectively decrease Chinese medicine syndrome scores，reduced white blood cells(WBC)and erythrocyte sedimentation rate(ESR)，and improved thyroid function，thyroid stimulating hormone(TSH)，triiodothyronine(T3)and thyroxine(T4)of patients with subacute thyroiditis，differences being significant(P ＜ 0.01，P ＜ 0.05)；and the treatment groups was better than the control group，difference being significant(P ＜ 0.05).Both groups could decrease the oxidation index malondialdehyde(MDA)，and increase the anti-oxidation index superoxile dismutase(SOD)，differences being significant(P ＜ 0.01，P ＜ 0.05)，and the treatment groups was better than the control group(P＜0.05).Conclusion：Yajiakang capsules has definite clinical effect in treating subacute thyroiditis in acute stage(heat-toxin congestion and excessiveness type)，and its functional mechanism may be reducing the oxidative stress levels of patients and enhancing the anti-oxidative stress function of body.