Abstract： Objective To detect the micro flow signals of carotid plaque by ultrasound B-flow imaging (BFI) and elucidate its relationship with acute cerebral infarction.Methods A total of 63 patients with carotid plaques were divided into 2 groups.acute cerebral infarction (ACI,n =48) and control (n =15).BFI was used to detect the micro flow signals of plaques and comparisons were made with the categorizing results of contrast enhanced ultrasound (CEU).The data were analyzed between two methods.Results The micro flow signals were detected in 15.7％ (22/140)patients in the ACI group vs.2.3％(1/44) in the control group.There were more signals in hypoechoic plaques.The detection percentage of micro flow in grade Ⅲ was significantly higher than that in grades Ⅰ and Ⅱ with CEU (P =0.005,P =0.027).No significant differences existed between grades Ⅲ and Ⅳ (P =1.000).Conclusion BFI can detect effectively the micro flow signals of carotid plaques and this characteristic is correlated with the symptoms of ACI.