Aim To investigate the correlation between serum levels of apolipoprotein AⅠ （ApoAⅠ）,apolipoprotein B （ApoB）,the ratio of apolipoprotein B to apolipoprotein AⅠ （ApoB/ApoAⅠ） and carotid plaque type in patients with acute myocardial infarction.Methods This study was carried out on 65 patients with acute myocardial infarction （case group） and 36 cases whose angiography were normal as control group.Serum ApoB and ApoAⅠ levels were measured,the ratio of ApoB/ApoAⅠ was calculated.All the patients were divided into three groups depending on the components of carotid plaque which was characterized by ultrasound: soft plaque,fibrous plaque and calcified plaque.All the data have been analyzed statistically.Results Soft plaque burden within the case group was significantly higher than that of the control group （P<0.001）.An increased level of ApoB and ApoB/ApoAⅠ ratio showed in the case group compared to the control group （P<0.05）.Compared with fibrous plaque and calcified plaque,serum ApoB levels and ApoB/ApoAⅠ ratio in the case group patients with soft plaque were higher （P<0.05）.Compared with fibrous plaque,serum ApoB levels and ApoB/ApoAⅠ ratio in the case group patients with soft plaque were higher （P<0.01）,ApoB and ApoB/ApoAⅠ ratio had certain accuracy in the diagnosis of soft plaques and the area under curve （AUC） of ROC were 0.753±0.067 and 0.701±0.071 respectively.Conclusions ApoB,ApoB/ApoAⅠ ratio and the type of plaque were markedly associated with acute myocardial infarction.In addition,ApoB and ApoB/ApoAⅠ ratio were related to the type of plaque which were classified according to the ultrasound.