Abstract: Objective: To observe the effects of different doses of ethanol administration on cardiac function and expression of B-cell lymphoma-2(Bcl-2) and Bcl-2-associated X protein(Bax) in rats. Methods: The SD rats were randomly divided into normal control group(normal group), low dose(2 g/kg·d^-1) ethanol administration group(low dose group) and high dose(8 g/kg·d^-1) ethanol administration group(high dose group). The effects of different doses of ethanol administration on heart rate(HR), mean left ventricular systolic pressure(mLVSP),mean left ventricular diastolic pressure(mLVDP), maximal rise velocity of left ventricular pressure(+dp/dtmax),maximal fall velocity of left ventricular pressure(-dp/dtmax), and expression of Bcl-2/Bax in rats were observed with a left ventricular intubation combined with an isoproterenol excitation and western blotting four weeks later.Results: Compared with the normal group, the HR,m LVSP, +dp/dtmax and-dp/dtmax were significantly decreased, the HR ratio, + dp/dtmax ratio and-dp/dtmax ratio were also significantly decreased at the dose of 25 ng/kg and above of isoproterenol, the expression of Bax protein was significantly increased,while the expression of Bcl-2 protein and Bcl-2/Bax was significantly decreased in the high dose group of rats(all P＜0.05). There was no significant change in the cardiac function indexes in the low dose group of rats, while the HR ratio, +dp/dtmax ratio and-dp/dtmax ratio were also significantly decreased at the dose of 50 ng/kg and above of isoproterenol, the expression of Bax protein was increased significantly, and Bcl-2/Bax was significantly decreased(all P＜0.05). Conclusion: High dose of ethanol administration can reduce cardiac function and cardiac function reserve of rats, while low dose of ethanol administration has no effect on cardiac function of rats,but can reduce cardiac functional reserve of rats, which may be related to their effects on the expression of cardiomyocyte apoptotic factors Bcl-2/Bax.