Aim To understand the paraoxonase(PON) activity in the patients with coronary heart disease,and the relationship between paraoxonase activity and coronary heart disease. Methods 106 cases having one or more than two branches narrow(≥50%), and 62 control group with no coronary artery narrow or narrow ≤50%,were diagnosed by coronary angiography.Blood paraoxonase(PON1) activity,superoxide dismutase(SOD) and malondialdehyde(MDA) levels were tested and analyzed by pheny acetate method and colorimetric method respectively in these two groups. Results Compared with the control group,PON1 activity and SOD were markedly decreased(p<0.05),MDA were increased in coronary heart disease(p<0.01);PON1 activity was positively associated with high density lipoprotein(HDL) cholesterol and SOD,was negatively associated with MDA.Compared with no coronary artery narrow or narrow ≤50%,the PON1 activity were markedly decreased(p<0.05),with the more severe lesion of coronary artery,the more lower PON1 activity. Conclusion PON1 activity were lower in the patients with coronary heart disease,lower PON1 activity was relative with the severe degree of coronary heart disease.