Objective To probe into protective action of taurine against exhaustive,exercise induced myocardial damage in rats.Methods Using the model of exhaustive exercise,the present study researches into the effects of taurine on the content of thyroid hormone(T3,T4)in serum and myocardium as well as T45'－ DI activity in myocardium of rats.Results The content of T3 in serum and myocardium,T45'－ DI activity in myocardium were significantly increased(P<0.01)while that of T4 in serum and myocardium had no significantly changed after exhaustive exercise,the supplement of taurine might significantly inhabits the changes.Conclusion Taurine could protect myocardium from exhaustive exercises induced damage by inhabiting hypermetabolism of thyroid hormone.