Abstract: AIM To observe and to analyze the effect of serum 25-hydroxyvitamin D3 level (25OHD3) on severity of coronary artery lesions. METHODS Two hundred and thirty-four patients with coronary heart disease diagnosed by selective coronary angiogram (CAG) were divided into two groups by their level of 25(OH)D3: non-deficiency group ［25(OH)D3≥20 ng/ml, n=33］ and 25(OH)D3 deficiency group ［25(OH)D3<20 ng/ml, n=201］. The degree of coronary artery stenosis was integrated by an internationally universal used Gensini Scoring System. The study used a fully automatic biochemistry analyzer to measure fasting blood glucose level (FPG), total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL-C) and low density lipoprotein (LDL-C). The investigation also used tandem mass spectrometry to measure 25(OH)D3 level. RESULTS The number of coronary lesions and Gensini score in the 25(OH)D3 deficiency group were significantly higher than those in the non-deficiency group (P<0.05). Logistic regression analysis showed that age, FPG and 25(OH)D3 level were independent relative factors of coronary artery lesions. Gensini integration was positively correlated with age, FPG, LDL-C and TC and it was negatively correlated with 25(OH)D3 level. CONCLUSION 25(OH)D3 level is a relative factor of the severity level of coronary artery lesions and they are negatively correlated.