Objective: To detect the changes of serum level of connective tissue growth factor (CTGF) in patients with ST-segment elevation myocardial infarction (STEMI) and to study the correlation between CTGF level and the maximal activity of creatine kinase-MB (CK-MB). Methods: Our research included 2 groups of patients: STEMI group and unstable angina (UA) group. All patients were treated in our hospital from 2013-07 to 2014-06,n=50 in each group. In STEMI group, the serum levels of CTGF were examined by ELISA at 24h, 2, 7, 14 days of onset, and in UA group, CTGF level was examined at 24h of onset. The CK-MB activity levels were measured in STEMI group at the same time points by immunosuppression method. Results: The serum level of CTGF in UA patients at 24 h of onset was (10.34 ± 2.00) ng/mL, and in STEMI patients were (16.76 ± 3.17) ng/mL at 24h, (29.87 ± 4.90) ng/mL at 2d, (45.02 ± 8.35) ng/mL at 7d and (31.61 ± 4.40) at 14d. The CTGF levels in STEMI group at different time points were all higher than UA group at 24h of onset,P<0.01. In STEMI group, the CTGF levels were increasing from 24h to 7d, then decreasing at 14d, allP<0.01. In STEMI group, the highest protein concentration of CTGF was positively related to the maximal activity of CK-MB at 7 days of onset (r=0.859,P=0.000). Conclusion: CTGF expression has been up-regulated in STEMI patients which might be related to myocardial ifbrosis. The protein level of CTGF is related to MI size, it shows certain predictive value in relevant patients.