Aim To assess the impact of right coronary artery (RCA) lesion on left ventricular ejection fraction(LVEF) in patients with left coronary artery (LCA) stenosis. Methods 1 000 cases with LCA stenosis were confirmed by coronary angiography. LVEF was compared between the group with isolated LCA stenosis and the group with both LCA and RCA stenosis. The group with isolated LCA stenosis included left anterior descending branch (LAD) stenosis, left circumflex branch (LCX) stenosis, left main artery (LM) stenosis and LAD+LCX stenosis. Results Compared with the accordant group with isolated LCA stenosis, LVEF decreased to different extent in every group with RCA stenosis. The changes in LAD+RCA group and LAD+LCX+RCA group were statistically significant (p<0.05 or 0.01). LVEF in LM+RCA group showed the greatest decrease, while in LCX+RCA group showed the slightest decrease without statistical significance. Conclusions RCA stenosis aggravates the left ventricular systolic function in patients with LCA stenosis, especially when the LCA lesion is located in LM or LAD or LAD+LCX.