This paper summarized clinical experience of treating recurrent subacute thyroiditis based on the theory of internal toxin. It is believed that the core pathogenesis of recurrent subacute thyroiditis is the accumulation of internal toxin. The dysfunction of the spleen in transportation leads to the internal retention of turbidity， which serves as the basis for the formation of toxins. The combination of fire， dampness， and toxins is the key to the disease mechanism. Prolonged accumulation of dampness and turbidity leads to the formation of phlegm， fire， and stasis， and prolonged accumulation of pathogenic factors transforms into secondary toxins. For patients with severe fire， dampness， and toxins， the treatment focuses on dispersing stagnated liver qi， invigorating spleen， and differentiation treatment of fire and water， using a self-designed Chaihu Jiedu Decoction （柴胡解毒饮）. For patients with spleen deficiency and toxin accumulation， the treatment focuses on invigorating the spleen， eliminating turbidity， and cutting off the source of toxins， using a self-designed Shiwei Baizhu Powder （十味白术散）. For patients with yang deficiency and toxin stagnation， detoxification is combined with warming yang， nourishing blood， and supporting toxin expulsion， using a self-designed Heyang Baidu powder （和阳败毒散）.