A total of 143 samples including 73 controls (43 males and 30 females, mean age of 62.49 ± 8.43 years) and 70 CAD patients (47 males and 23 females, mean age of 65.00 ± 10.24 years) were randomly selected to detect the serum C3 levels. This evidence concerns the gene C3 and coronary artery disorder.