Abstract: AIM To study the factors influencing the formation of coronary collateral circulation( CCC)when acute myocardial infarction( AMI) occurs. METHODS One hundred and forty-seven AMI patients underwent coronary angiography( CAG) within 24 h after onset of AMI. Patients were divided into two groups( good and poor) according to the Rentrop collateral circulation. Patients in the good group had good collateral circulation( grades II and III) and patients in the poor group had poor collateral circulation( grade 0,I). Clinical data and results of coronary angiography were analyzed and compared between groups. RESULTS Formation of coronary collateral circulation was negatively correlated with diabetes and was positively correlated with the duration of pre-infarction angina( > 3 months) and numbers of diseased coronary vessels,regardless of age,gender,smoking,cholesterol,hypertension. CONCLUSION Duration of pre-infarction angina( > 3 months) and number of diseased coronary vessels are the factors conducive to the formation of collateral circulation. Diabetes is not conducive to the formation of collateral circulation in AMI patients.