Objective To explore the relationship between Helicobacter pylori(Hp) infection and serum homocysteine(Hcy) level ,carotid intima-media thickness and plaque stability in carotid atherosclerosis cases .Methods 206 carotid atherosclerosis pa-tients were collected between March 2012 and January 2013 in our hospital .According to the results of 14C urea breath test ,all the subjects were divided into Hp infection group and non-Hp infection group .And according to the degree of carotid artery atheroscle-rosis ,patients with Hp infection were divided into carotid intima-media thickness thickening group ,stable plaque group and unstable plaque group .The serum Hcy level was detected by enzymatic cycling method ,and the relationship between Hp infection and serum Hcy level ,carotid intima-media thickness and plaque stability in carotid atherosclerosis cases were analyzed .Results Serum Hcy level and carotid carotid intima-media thickness of patients with carotid atherosclerosis in Hp infection group were higher than those in non-Hp infection group(P<0 .01) .The differences in constitution ratio of patients with different types of carotid atherosclerosis in Hp infection group and non-Hp infection group was statistically significant(χ2 =15 .939 ,P=0 .000 3) .In Hp infection group , there were statistically of serum Hcy levels among carotid intima-media thickness thickening group ,stable plaque group and unsta-ble plaque group(P<0 .01) .Linear correlation analysis showed that the serum Hcy level and carotid intima-media thickness were positively correlated in Hp infection group(r=0 .731 ,P<0 .01) .Conclusion Hp infection is likely to promote the development and progression of atherosclerosis through influencing Hcy metabolism and increasing carotid intima-media thickness and instability of carotid atherosclerotic plaque .