Aim To investigate the serum levels of 25(OH)D and analyse its correlation with the severity of coronary artery stenosis in patients with coronary heart disease. Methods 150 patients underwent coronary angiography, all selected objects in general were recorded, including gender, age, history of hypertension and diabetes and so on. Biochemical parameters were measured by immune nephelometry dialysis, including fasting glucose, low density lipoprotein cholesterol (LDLC), serum calcium (Ca²⁺). The serum 25(OH)D levels were measured by high performance liquid chromatography-tandem mass spectrometry in all patients. They were divided into normal control group and coronary artery lesion group according to the angiography results. The coronary artery lesion group was divided into mild, moderate and severe subgroups according to SYNTAX score. Results The serum 25(OH)D levels was 13.87±7.16 μg/L in patients with coronary heart disease and 21.67±7.38 μg/L in normal control group. The serum 25(OH)D levels in patients with coronary artery lesion was lower than that of control group (P<0.05), and gradually decreased as the severity of coronary artery lesions became more severe (P<0.05). In SYNTAX scores ≥33 group,SYNTAX scores 23～32 group and SYNTAX scores ≤22 group the serum 25(OH)D levels was significantly lower than that of normal control group (P<0.05). With the increase of SYNTAX scores, the serum 25(OH)D levels decreased obviously(P<0.05). There was a negative correlation between the serum 25(OH)D levels and the coronary artery lesions(r=－0.328,P=0.019). The levels of LDLC, blood sugar and serum calcium was 2.90±0.98 mmol/L, 5.85±1.46 mmol/L, 2.09±0.22 mmol/L. Bivariate correlation analysis of 25(OH)D level with the age, LDLC, blood sugar and serum calcium revealed no obvious correlation. Conclusion The serum 25(OH)D levels decrease significantly in patients with coronary heart disease, and its level is closely related to the degree of coronary artery lesions.