Background: This study measured the change in connective tissue growth factor levels after the onset of unstable angina and ST- segment elevation myocardial infarction, and studied its correlation with peak creatine kinase-MB (CK- MB) enzyme. It also discussed the significance of myocardial fibrosis after myocardial infarction. To detect the serum levels of connective tissue growth factor in patients with ST-segment elevation myocardial infarction and its relationship with the maximum level of CK-MB. Methods: We selected 50 patients with ST-segment elevation myocardial infarction and 50 patients with unstable angina. Connective tissue growth factor levels were examined 24 h, 2 d, 7 d, and 14 d after the onset of ST-segment elevation myocardial infarction, and within 24 h for unstable angina, using enzyme-linked immunosorbent assay (ELISA). The maximum level of CK-MB was detected by immunosuppression. Results: The serum level of connective tissue growth factor in the unstable angina patients was 10.34 ±2.00 ng/ mL, and the levels in the ST-segment elevation myocardial infarction patients were 16.76 ±3.17 ng/mL at 24 h, 29.87 ±4.90 ng/mL at 2 d, 45.02±8.35 ng/mL at 7 d, and 31.61 ±4.40 ng/mL at 14 d. Compared with the unstable angina patients, the connective tissue growth factor levels in the ST-segment elevation myocardial infarction patients were significantly higher since day 1 (p < 0.01). The maximum level of CK-MB was correlated with connective tissue growth factor levels at 7 d (r = 0.859, p = 0.000). Conclusions: Connective tissue growth factor was significantly expressed in the ST-segment elevation myocardial infarction patients, indicating that it might play an important role in myocardial fibrosis.