Abstract： Objective To explore the relationship between thyroid hormone (TH) changes and cardiac function in patients with congestive heart failure (CHF). Methods In CHF group (36 patients with CHF) and control group (23 non-CHF patients), three plasma triiodothyronine ( T3 ), four-triiodothyronine ( T4 ), thyroid iodine against three the original acid ( rT3 ) and thyroid stimulating hormone (TSH) were determined by radioimmunoassay ; cardiac output ( CO), left ventricular ejection fraction ( LVEF), left ventricular end diastolic volume ( LVEDV), left ventricular end systolic volume (LVESV) by echocardiography. Results In CHF group T3 levels and LVEF,CO were significantly lower than the control group[T3 : ( 1.6 ±0.2) nmol/L, ( 1.5 ±0.2)nmol/L vs (2.0 ±0.3)nmol/L,LVEF:(54.4±8.3)％,(51.3±11.1)％ vs (59.0±8.9)％,CO:(4.3 ±2.6)L/min,(4.1±2.6)L/min vs (5.5 ±1.6)L/min,P＜0.05 or P＜0. 01]; rT3, LVEDV and LVESV increased significantly[rT3 :(0.6 ± 0.3 ) nmoL/L, (0.6 ± 0.4) nmol/L vs (0.3 ± 0.1 ) nmol/L, LVEDV : (202 ± 46) ml, ( 234 ± 65 ) ml vs ( 175 ±53 ) ml, LVESV : ( 149 ± 57 ) ml, ( 160 ± 59) ml vs ( 124 ± 56 ) ml, P ＜ 0.01], and with the degree of heart failure increased,the more obvious changes. Conclusion TH changes have great significance on cardiac function damage,treatment and prognosis of patients with CHF.