Aim To investigate the impact of helicobacter pylori (HP) infection and cytotoxin associated protein A toxin of HP (HP-CagA) on serum matrix metalloproteinase-9 (MMP-9) in patients with coronary heart disease (CHD), and the relationship between HP-CagA and coronary lesion. Methods 105 patients with CHD were chosen in this trial, including 35 patients with acute myocardial infarction (AMI), 35 patients with unstable angina pectoris (UAP) and stable angina pectoris (SAP), while 35 inpatients with normal coronary artery (NCA) in the same period. The level of serum MMP-9, the positive rate of HP-IgG antibody and HP-CagA-IgG antibody were measured by enzyme-linked immunosorbent assay (ELISA) and the correlation between the level of serum MMP-9, the positive rate of HP-IgG antibody, the positive rate of HP-CagA-IgG antibody and coronary angiography Gensini score were analyzed respectively. The differences between CHD patients with HP infection and without HP infection were compared, and the differences between CHD patients with positive HP-CagA-IgG and negative HP-CagA-IgG were compared. Results The four groups showed significant differences in serum MMP-9 level (all P＜0.05), among them, AMI group＞UAP group＞SAP group＞NCA group (all P＜0.05). Compared to NCA group, AMI group, UAP group and SAP group were higher in Gensini score (all P＜0.05). There was significant correlation between serum MMP-9 level and Gensini score in each group (all P＜0.05). The positive rates of HP-IgG in SAP group, UA group, AMI group and NCA group were 40%, 57.1%, 74.3% and 28.6%, respectively; among them, AMI group＞UAP group＞SAP group＞NCA group (all P＜0.05); the patients with positive HP-IgG in each group showed the higher levels of MMP-9 than those with negative HP-IgG (all P＜0.05); there was significant correlation between the positive rate of serum HP-IgG and Gensini score in each group (all P＜0.05). The positive rates of HP-CagA-IgG in SAP group, UAP group, AMI group and NCA group were 17.1%, 31.4%, 40.0% and 11.4%, respectively; among them, AMI group＞UAP group＞SAP group＞NCA group (all P＜0.05); the patients with positive HP-CagA-IgG in each group showed the higher levels of MMP-9 than those with negative HP-CagA-IgG, there were statistical differences (all P＜0.05); there was significant correlation between the positive rate of serum HP-CagA-IgG and Gensini score in each group (all P＜0.05). The serum MMP-9 level among each group, HP-IgG(＋)CagA-IgG(＋) subgroup＞HP-IgG(＋)CagA-IgG(－) subgroup＞HP-IgG(－)CagA-IgG(＋) subgroup (all P＜0.05); the positive rate of serum HP-IgG and the positive rate of serum HP-CagA-IgG were significantly correlated with the serum MMP-9 level and Gensini score, especially the positive rate of serum HP-CagA-IgG was more closely related to the serum MMP-9 level and Gensini score (all P＜0.05). Conclusion HP infection especially HP-CagA infection, might be related to the occurrence and development of CHD through the large secretion of MMP-9 by endothelial cells, which might be new indicators of the severity of the coronary artery in future.