Objective:To investigate the therapeutic effects of catalpol on hyperthyroidism in rats. MethodsThe hyperthyroid model was established by levothyroxine sodium (L-T4) with subcutaneous injection at dose of 280 ng/g. After successful modeling,the model rats were divided into the model group,thiamazole group (10 μg/g),propylthiouracil group (40 μg/g) and catalpol groups with low- (10 μg/g),middle-(20 μg/g) and high-(40 μg/g) dose. After treatment for 21 days,the heart rate,heart weight index and spleen index of rats in each group were measured. The levels of triiodothyronine (T3),thyroxine (T4),free triiodothyronine (FT3),free thyroxine (FT4),thyroid stimulating hormone (TSH),thyroid microsomal antibody (TMAB),thyroglobulin antibody (TGAB),tumor necrosis factor-α (TNF-α),interleukin-6 (IL-6),interleukin-2 (IL-2) and interleukin-10 (IL-10) were detected by enzyme-linked immunosorbent assay .  Results:Compared with the model group,the heart rate,the levels of T3,T4,FT3,FT4,TGAB,IL-2/IL-10,the index of whole heart,left heart and spleen were significantly decreased in the catalpol groups with middle- and high-dose (P<0.05),while the TSH level was increased significantly (P<0.05).  Conclusion:Catalpol shows certain improving and therapeutic effects on hyperthyroidism.