Objective：This study aims to compare the vascular function of the descending branch of lateral circumflex femoral artery（DBLCFA）and the internal mammary artery（IMA）of coronary artery bypass grafts，according to the vasoconstrictor and diastolic effects of the two drug pharmacological response to evaluate its spasticity characteristics and endothelial function. Methods：The 33 descending branches of the external circumflex femoral artery and 31 internal mammary arteries of 20 patients with coronary artery bypass grafting were balanced in the organ bath. Vasoconstriction was detected by receptor-mediated vasoconstrictors endothelin-1，angiotensin Ⅱ and thromboxane A2 mimic U46619. Acetylcholine was used to test endothelium-dependent relaxation，and nitroglycerin was used to test endothelium-independent relaxation. The maximum contraction or relaxation response of the two arteries，and the effective concentration that caused 50% of the maximum contraction or relaxation response were compared. Results：In the contraction caused by endothelin-1，angiotensin Ⅱ and U46619，the reactivity of DBLCFA was higher than that of IMA，respectively［（0.94±0.09）g vs.（0.57±0.08）g，P=0.012；（0.88±0.13）g vs.（0.24±0.05）g，P < 0.001；（4.95±0.57）g vs.（1.86±0.30）g，P=0.001］. When converted into the percentage of contractile force caused by 100 mmol/L KCl，there was no significant difference between the two groups. There was no significant difference in the effective concentration of 50% of the maximum contractile response caused by endothelin-1 and angiotensin Ⅱ. The effective concentration of 50% of the maximum contractile response caused by U46619 of DBLCFA was higher than that of IMA. There were no significant differences between receptor-mediated endothelium-dependent relaxation and non-endothelium-dependent relaxation between the two types of blood vessels. There were no significant differences in the effective concentration of 50% of the maximum diastolic response between the two arteries. Conclusion：DBLCFA has a higher pharmacological response to vasoconstrictors than the IMA，suggesting that it is more prone to vasospasm. The diastolic response of DBLCFA is similar to that of IMA，but DBLCFA is more prone to spasm. So its vascular function is inferior to that of the IMA. But when the use of IMA is limited，DBLCFA may be an option for the surgeon.