Aim To explore the relationship between serumγ-glutamyl transferase (GGT) levels and coronary complexity, severity and extent. The interaction of serum GGT with the traditional risk factors of acute coronary syndrome (ACS) was evaluated.Methods 413 consecutive patients with ACS who underwent coronary angiography were enrolled. Baseline serum GGT levels were measured and Gensini score was calculated from the study population. All patients underwent test of GGT, clinical characteristics, blood lipid, brain natriuretic peptide (BNP), blood urea nitrogen, serum creatinine, uric acid, and measuring risk factors.Results Serum GGT levels demonstrated an increase from low Gensini tertile to high tertile. In multivariate analysis, a significant positive correlation was found between logGGT levels and the different number of diseased coronary vessels, diabetes mellitus, total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDLC) and high sensitive C-reactive protein (hs-CRP) (P<0.05). TC was the strongest influence on logGGT. Further studying the relations between coronary stenosis severity (Gensini score) and serum GGT as well as the traditional risk factors of ACS, the results showed logGensini had a significant positive correlation with serum GGT, age, ALT, smoking, the different number of diseased coronary vessels (P<0.05).Conclusion Serum GGT involved the development of coronary plaque, serum GGT tested has important clinical values in assessing the severity of coronary artery disease.