Objective To evaluate the application of serological detection of Chlamydia pneumonia (Cpn) in patients with acute coronary syndrome (ACS) .Methods From Oct .2012 to Oct .2013 ,80 patients with ACS (ACS group) and 80 healthy subjects (control group) were enrolled and detected for Cpn DNA .According to the detected results ,ACS patients were divided to chlamydia group and non‐chlamydia group .Serum levels of tumor necrosis factor α(TNF‐α) ,C reaction protein (CRP) ,intercellular cell adhe‐sion molecule‐1 (ICAM‐1) and lipoprotein were also detected .Results In ACS group ,53 cases were Cpn positive and 27 cases were Cpn negative ,and in control group ,7 cases were Cpn positive and 83 cases were Cpn negative ,which were with statistical difference between the two groups (P<0 .05) .Serum levels of TNF‐α,CRP ,ICAM‐1 ,total cholesterol ,triacylglycerol and low density lipo‐protein cholesterol were higher in chlamydia group and that of high density lipoprotein cholesterol was lower than non‐chlamydia group (P<0 .05) .Conclusion Chlamydia pneumoniae infection might be correlated with ACS .Chlamydia pneumoniae infection could be involved in disease development by increasing levels of inflammatory cytokines in ACS patients ,and further improve serum lipid levels .