Objective: To observe the clinical efficacy of “Yajia Formula” for the treatment of subacute thyroiditis of the blood heat with blood stasis pattern.Methods Sevnety cases with subacute thyroiditis were randomized into treatment group and control group, with 35 cases in each group.Control group was treated with Prednisone Acetate Tablets orally, and treatment group was treated with “Yajia Formula” orally, with the course of 2 months.The clinical efficacy, adverse reactions, recurrence rate were observed, and the effect of individual symptoms, changes of related blood biochemical indexes (including leukocyte, neutrophil, C-reactive protein, erythrocyte sedimentation rate), and related thyroid gland indicators (FT3, FT4, TSH) were compared and analyzed.Results ① Sixty patients finished the experiment at the end of treatment, 30 cases in the treatment group and 30 cases in the control group.② The total effective rate was 90.00% in the treatment group and 73.33% in the control group, with a difference between the two groups(P<0.05).③ In both groups, the individual symptoms were improved, with significant difference between before and after treatment (P＜0.05).After treatment, there were significant differences in goiter, weakness, hidrosis, pain limbs, poor appetite between the two groups, and the improvement in the treatment group was superior to that of the control group (P＜0.05); no significant difference was found in fever, thyroid pain, tremble, pharyngalgia between the two groups (P＞0.05).④ In both groups, there were significant differences in leukocyte, neutrophil, C-reactive protein and erythrocyte sedimentation rate between before and after treatment (P＜0.05).After treatment, there were significant differences in the value of leukocyte, neutrophil, C-reactive protein and erythrocyte sedimentation rate between the two groups (P＜0.05).⑤ In both groups, there were significant difference in the levels of FT3, FT4 and TSH between before and after treatment (P＜0.05); After treatment, no significant difference was found in the levels of FT3, FT4 and TSH between the two groups (P＞0.05).⑥ The adverse effective rate of the treatment group was superior to that of the control group (P＜0.05).⑦ The recurrence rate in the treatment group was superior to that of the control group (P＜0.05).Conclusion “Yajia Formula” can relieve the clinical symptoms and reduce inflammation reaction in treating subacute thyroiditis of the blood heat with blood stasis pattern with less adverse reactions and recurrence rates.