Myocardial ischemia (MI) refers to a pathological state of the heart caused by reduced cardiac blood perfusion, which leads to a decreased oxygen supply in the heart and an abnormal myocardial energy metabolism. Acute myocardial ischemia (AMI) has posed a significant health risk for humans. Allium macrostemon Bunge (AMB), a popular traditional Chinese medicine, is used for MI treatment. The therapeutic effects of AMB were assessed and the detailed mechanisms of AMB for AMI treatment were investigated. We characterized the metabonomic variations in rats from the sham surgery, AMI, and AMB-pretreated AMI groups through a combination of nuclear magnetic resonance (NMR) spectroscopy and multivariate statistical analysis. Thirty-five metabolites including carbohydrates, a range of amino acids, and organic acids were detected. The (1)H NMR spectra of the rat serum were analyzed using the principal component analysis (PCA) and orthogonal projection to latent structures discriminate analysis (OPLS-DA). Results showed that AMI induced some physiological changes in rats and also led to metabolic disorders related to glycolysis promotion, amino acid metabolism disruption, and other metabolite metabolism perturbation. AMB pretreatment reduced the AMI injury and maintained metabolic balance, possibly by limiting the change in energy metabolism and regulating amino acid metabolism. These findings provide a comprehensive insight on the metabolic response of AMI rats to AMB pretreatment and are important for the use of AMB for AMI therapy.