Objective: To examine the effect of Yuxingeng fluid (愈心梗液, YXGF) on myocardial energy metabolism in Wistar rats with acute myocardial infarction (AMI) by observing the ultrastructure of mitochondria and the enzyme activities of rat myocardial adenosine triphosphate (ATP), succinate dehydrogenase (SDH), acid phosphatase (ACP), alkaline phosphatase (ALP) and the content of glycogen. Methods: AMI models were established by ligature of left anterior descending coronary artery and then the rats with AMI were randomly divided into 7 groups: namely, blank group, model group, sham-operated group, captopil group, high-dose YXGF group, middle-dose YXGF group and Iow-dose YXGF group. From the next day after modeling, the rats were given YXGF through gastrogavage which lasted for 4 weeks. And then, the ultrastructure of mitochondria was observed by electronic microscope and the enzyme activities of ATP, SDH,ACP, ALP and the content of glycogen were determined. Results: Compared with model group, the other three groups of high-dose YXGF, middle-dose YXGF, Iow-dose YXGF and captopril group could protect the ultrastructure of mitochondria and significantly increase enzyme activities of ATP, SDH, ACP, ALP and the content of glycogen (P＜0.01). Conclusion: YXGF can protect mitochondria and increase myocardial enzyme activities and the content of glycogen, which may be one of the mechanisms intervening in the pathological course of the early ventricular remodeling in rats with AMI.