Objective To explore the diagnostic value of 64-slice spiral CT coronary angiography (CTA) in coronary stenosis in patients with type 2 diabetes mellitus (T2DM) complicated with coronary heart disease. Methods The clinical data of 140 patients with T2DM suspected as coronary heart disease in our hospital were retrospectively analyzed. All patients were given CTA and selective coronary arteriography (CAG). CAG was used as the gold standard to evaluate the sensitivity, specificity, positivity (negative) predictive value and Kappa value (consistency) of CTA in the screening of coronary heart disease, diseased vessels and luminal stenosis. Results The sensitivity, specificity, accuracy, positive predictive value, negative predictive value and Kappa value of CTA in the screening of coronary heart disease were 0.953, 0.912, 0.943, 0.971, 0.861 and 0.848 respectively, and CTA had good consistency with CAG. The consistency of CTA and CAG was common in the diagnosis of left main artery (LM) lesions, and was good in the diagnosis of left anterior descending (LAD), left circumflex (LCX) and right coronary artery (RCA) lesions. CTA had high sensitivity in the diagnosis of mild, moderate and severe luminal stenosis. Conclusion CTA has high accuracy in the screening of patients with T2DM and coronary heart disease, and it can accurately determine the vascular lesions and stenosis degree.