Objective To investigate the infection of Helicobacter pylori infection on the serum concentration of homocysteine (Hcy) and its relationship with coronary heart disease (CHD) .Methods 159 cases of patients with CHD were selected as the re‐search subjects .They were divided into two groups :infection group and non‐infection group ,according to the results of 14 C‐urea breathe test .And they were also divided into three groups :negative group ,mild infection group and severe infestation group ,accord‐ing to the severity of infection .The CHD patients infected Helicobacter pylori were divided into three groups:low risk group ,mod‐erate risk group and high risk group ,according to SYNTAX scores .The serum Hcy concentration was determined by cyclic enzy‐matic method .Results Comparing with non‐infection group ,the serum Hcy concentration significantly increased in infection group (P<0 .01) .With the aggravation of Helicobacter pylori infection ,the serum Hcy concentration increased .There were significant difference among negative group ,mild infection group and severe infestation group (P<0 .01) .In the CHD patients infected Heli‐cobacter pylori ,the serum Hcy concentration also increased with the aggravation of the severity of coronary lesion .And there were significant difference among low risk group ,moderate risk group and high risk group (P<0 .01) .Conclusion Helicobacter pylori plays a role in the incidence and development of CHD through increasing the serum Hcy concentration .