Objective: To investigate the relationship between serum levels of brain natriuretic peptide(BNP), carbohydrate antigen 125(CA125), thyroid hormone(TH) and cardiac function in patients with chronic heart failure(CHF). Methods: A total of 120 patients with CHF, who were treated in Affiliated Hospital of Inner Mongolia Medical University from December 2015 to December 2017,were selected as the subjects. The cardiac function grading of the patients was New York Heart Association(NYHA) I/II with 51 cases;NYHA III with 39 cases, NYHA IV with 30 cases. Another 40 healthy volunteers, who were received physical examination in this hospital during the same period, were selected as control group. The levels of serum BNP, CA125 and TH were measured in all subjects, and their relationship with left ventricular ejection fraction(LVEF) and left ventricular end-diastolic diameter(LVEDD) was analyzed. Results: The levels of serum BNP and CA125 in the patients with different cardiac functions were significantly higher than those in the control group,and the levels of BNP and CA125 were increased with the increasing of NYHA grading(P<0.05). The level of serum T3 in the patients with NYHA III and NYHA IV was significantly lower than that in the control group, and level of T3 was gradually decreased with the increasing of NYHA grading, the difference was statistically significant among all groups(P<0.05). Pearson analysis showed that levels of serum BNP and CA125 were negatively correlated with LVEF(P<0.05), and there were positively correlated with LVEDD(P<0.05). The level of serum T3 was positively correlated with LVEF(P<0.05), and there was negatively correlated with LVEDD(P<0.05). Conclusion:Serum BNP, CA125 and T3 levels in the patients with CHF are closely related to cardiac function, and the combined detection of the three elements has great value in the clinical diagnosis and condition judgement of CHF. [ABSTRACT FROM AUTHOR]