Objective · To explore the relationship between serum vitamin D level and coronary artery lesion severity and short-term prognosis in coronary artery disease (CAD) patients. Methods · A total of 323 CAD patients diagnosed according to coronary angiogram were selected and the coronary artery lesion severity was evaluated by using Gensini score. Clinical data was collected and serum level of vitamin D and other indicators were determined for statistical analysis. Results · All patients were divided into tertile according to Gensini score. The level of serum vitamin D concentration was significantly different from the lowest tertile to the highest tertile (P=0.000). Serum vitamin D level was negatively correlated with Gensini score in CAD patients (r=-0.182, P=0.001). Multivariate linear analysis showed that vitamin D level was an independent predictor of Gensini score (β=-0.795, P=0.000). There was no difference in the incidence of major advanced cardiovascular events between vitamin D deficiency patients and normal vitamin D level patients (2.05% vs 3.17%, P=0.202) after (18.14±3.04) months' follow-up. Conclusion · There is an independently negative correlation between serum vitamin D and coronary artery lesion severity in CAD patients.