Aim To investigate the relationship between carotid atherosclerosis,C-reactive protein(CRP) and acute cerebral infarction. Methods Histological changes of carotid artery were observed by color Doppler and the serum CRP were evaluated in 86 patients with acute cerebral infarction,compared with the control group which contained 40 non-cerebral infarction patients. Results Incidence of carotid artery endothelial plaque in patients with acute cerebral infarction was significantly higher than those of control group(p<0.01). In patients with acute cerebral infarction,soft plaque and mixed plaque were predominant while hard plaque were predominant in control group,there were significant difference between the two groups(p<(0.01)).Serum CRP levels in patients with cerebral infarction were obviously higher than those of control group(p<0.01).Serum CRP levels in 5 groups were respectively 9.80±2.43 mg/L,10.72±2.55 mg/L,7.46±2.54 mg/L,6.38±1.96 mg/L and 6.15±1.71 mg/L,which histological changes of carotid artery endothelial were soft plaque,mixed plaque,hard plaque,crude endothelium and normal,the levels of serum CRP in soft plaque group and mixed plaque group were higher than those of hard plaque group,crude endothelium group and nomal group(p<0.01). Conclusion Incidence of carotid artery endothelial plaque and serum CRP levels were obviously increased in patients with acute cerebral infarction.Increase of the serum CRP levels can represent the properties and stability of carotid artery plaque.