To explore the efficacy，safety and mechanism of Xiaojin capsule in the treatment of nodular Hashimoto's thyroiditis.Methods:A total of 240 patients from Mar.2015 to Feb 2016 in Jinzhou Central Hospital with nodular Hashimoto's thyroiditis were included who were characterized by qi stagnation，blood stasis，phlegm coagulation，and thyroid function normal or reduce.They were randomly assigned to the observation group or the control group evenly according to the random number table.The control group was treated with Levothyroxine Sodium Tablets，and the initial dose was 25 μg/d，and then adjusted to 50 ug/d after 2 weeks.Then the thyroid function was rechecked once a month，and the dosage was adjusted according to the thyroid function.The observation group was treated with Xiaojin capsule on the basis of the control group，9 grains/d (0.35 g/ granules)，4 after breakfast，5 after dinner，21 days as a course of treatment，and continued for the next course after withdrawal for 7-10 days.The thyroid function and autoantibody were reexamined every month.When the thyroid function and antibody level were restored to normal for 3 months or the level of the 9 month antibody remained unchanged，it was reduced to 7 tablets daily，3 after breakfast and 4 after dinner.The total treatment time was 12 months.This efficiency，maximum thyroid nodule length，TCM symptom score，complete remission rate of TCM symptoms，thyroid function，thyroid autoantibody，IL-8，IL-10 levels，the incidence of thyroid cancer and the incidence of adverse events were observed.Results:A total of 231 patients completed the study，of which 115 cases were completed in the control group，2 cases were lost，3 cases were withdrawn.116 cases were completed in the observation group，3 cases were lost and 1 case was withdrawn from the study.The shedding rate and lost visit rate were comparable in the two group (P>0.05).There were no significant differences in sex，age，course of disease，TCM syndrome score，thyroid function，thyroid autoantibody level and color Doppler ultrasound before treatment in the two groups (P>0.05).The clinical cure rate of the observation group was significantly higher than that of the control group (P<0.05).After treatment，the length of the largest nodule in the observation group was narrowed more significantly (P<0.05).The disappearance rate of thyroid nodules in the observation group (40.5%) was significantly higher than that in the control group (P<0.05).The reduction of clinical symptom scores in the observation group was significantly higher than that in the control group (P<0.05).The thyroid function of the two groups was significantly improved (P<0.05)，and there was no significant difference between the two groups (P>0.05).The level of thyroid autoantibody in the observation group was significantly decreased (P<0.05)，but the control group did not significantly change (P>0.05)，and there was a significant difference between the groups (P<0.05).The level of IL-8 in the observation group decreased significantly (P<0.05)，while that in the control group did not change significantly (P>0.05)，and the difference between the two groups was statistically significant (P<0.05).The level of IL-10 in the observation group increased significantly (P<0.05)，while that in the control group did not change significantly (P>0.05)，and the difference between the two groups was statistically significant (P<0.05).After treatment，the incidence of thyroid cancer in the observation group was significantly lower than that in the control group (P<0.05).The incidence of adverse events in the observation group was significantly lower than that in the control group (P<0.05).Conclusion:Xiaojin capsule can regulate the balance of Th1/Th2 and reduce the level of thyroid autoantibody.It is effective and safe in treating nodular Hashimoto's thyroiditis with normal or reduced thyroid function，combined with levothyroxine sodium.It is worthy of promotion in clinical practice.