Objective: To evaluate value of application of intravascular ultrasound imaging (IVUS) in diagnosing borderline lesions in left anterior descending artery (LAD) and left main coronary artery (LM). Methods: According to results of coronary angiography (CAG) in 60 cases with coronary borderline lesions, including 20 cases in LM, 20 cases in proximal segment of LAD and 20 cases in middle segment of LAD, the diagnostic value of IVUS in coronary borderline lesion was evaluated. Results: Compared with CAG, mean diameter stenosis rate of each coronary artery [LM: (65.3l±7.81) % vs. (75.28±8.89) %，proximal segment of LAD: (66.67±8.79) % vs. (78.89±7.88) %，middle segment of LAD: (71.55±6.83) % vs. (75.3l±7.81) %, P<0.01 all] significantly increased in IVUS. The differences of detection rate of plaque calcification and plaque rupture were no significant between CAG and IVUS（＞0.05）. Conclusion: Different degrees of underestimation of coronary artery stenosis exist in CAG, especially in proximal segment of LAD. IVUS can be an effective complement to CAG.