Aim To elucidate the characteristics of carotid plaques in patients between acute coronary syndrome (ACS) and atherothrombotic cerebral infarction (ACI). Methods 100 patients (50 patients with single-vessel coronary artery disease (SVD) and the others with multivessel coronary artery disease (MVD) ) with ACS and fifty-six patients with ACI were enrolled in this study, carotid artery ultrasound-based atherosclerotic parameters of all patients were measured. Results Carotid atherosclerotic plaques in patients with ACS and ACI were multiple in the bilateral carotid sinus, and more common with hard spot. The incidence of plaque in ACS patients with MVD was higher than that SVD (P<0.05), similar to those with ACI. The incidence of unstable plaque and stenosis in patients with MVD and ACI was higher than those with SVD (P<0.05). Conclusions High-frequency ultrasound findings showed similar characteristics of carotid plaque in ACS and ACI patients. The similarity of cervical plaque features in MVD patients was more obvious.