Objective To evaluate the effects of catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) system on the range and severity of coronary artery lesions in patients with abnormal glucose metabolism. Methods This study included 766 patients with abnormal glucose metabolism. Levels of fasting blood lipids, blood glucose, CAT, SOD, GSH, glutathione reductase (GR), and glutathione peroxidase (GSH-Px) were measured in all the patients. Coronarography was performed, and the degree of the lesions in each coronary artery was quantitatively analyzed using the Gensini scoring system. Results In patients with impaired glucose regulation and diabetes, the number of coronary artery branches with stenosis and the Gensini scores were inversely correlated with the plasma levels of CAT, SOD, GSH, GH, and GSHPx (P < 0.001). Patients were grouped according to the Gensini scores. As the scores increased, the levels of CAT, SOD, GSH, GSH-Px, and GR gradually decreased. Logistic gradual regression analysis showed that GSH-Px and CAT were independent risk factors associated with the coronary artery lesions in three or more branches. Conclusions Decreased plasma levels of CAT, SOD, GSH, GR, and GSH-Px were inversely correlated, at least to some extent, with the extent of coronary artery lesions. Particularly, GSH-Px and CAT were independent risk factors associated with coronary artery lesions involving three or more branches. This suggests that long-term hyperglycemia leads to enhancement of oxidative stress.