Aim To investigate the relativity of different kinds of leukoaraiosis （LA）, stability of carotid atherosclerosis plaque and serum Lp-PLA2. Methods All LA patients were divided into three groups according to their brain MRI: periventricular type group, subcortical type group and mixed type group. Carotid atherosclerosis plaques were detected by carotid artery ultrasonography and divided into stable palques and vulnerable plaques by their ultrasonographic images. Plaque score was calculated with crouses method. Serum Lp-PLA2 concentration was detected by acid hydrolysis of the substrate color method. Results Among the three groups, there were no statistically significant differences in the items including age, gender, blood pressure, glucose, low density lipoprotein and uric acid. The positive rates of carotid atherosclerosis plaque of subcortical type group and mixed type group were both absolutely higher than those of periventricular type group （P＜0.01）. There were marked difference of serum Lp-PLA2 concentration between each group （P＜0.05）. Serum Lp-PLA2 concentration of subcortical type group was the highest and serum Lp-PLA2 concentration of periventricular type group was the lowest. Serum Lp-PLA2 concentration of subcortical type group was postively corelated to the scores of their vulnerable plaque （r＝0.270, P＜0.05）. Conclusions Serum Lp-PLA2 may be related to instability of carotid atherosclerosis plaque and can cause plaque rupture through imflammatory mechanisms, which plays an importment role in the process of occurence and development of LA of subcortical type group.