: To explore the role and mechanism of miR-27b-3p in treating infantile hemangiomas (IHs) with propranolol and to clarify the cause of the poor efficacy of propranolol in IHs. : Human umbilical vein endothelial cells (HUVECs) were used as the research model and were treated with 0, 15, 30, 45, 60, and 90 μM of propranolol to explore the best concentration. RNA interference technology was used to regulate the expression of miR-27b-3p. CCK-8, TUNEL, and flow cytometry detected cell proliferation and apoptosis levels. Real-time PCR was used to detect the expression of miR-27b-3p and apoptosis pathway-related mRNA, and Western blotting was used to detect the expression of apoptosis-related proteins. The target relationship between miR-27b-3p and Apaf-1 was analyzed using a double Luciferase report. : The most significant inhibitory effect on cell activity of propranolol is at a dose of 30 μM. After propranolol treatment, the expression of miR-27b-3p was downregulated, and the expression of the apoptotic factors Apaf-1, PARP, caspase-9, and caspase-3 was upregulated, which was consistent with the results after the deletion of miR-27b-3p. However, after upregulation of miR-27b-3p, the level of and the expression of apoptotic factors was inhibited. "targetscan.org" gene database analysis found that miR-27b-3p matched the 3'-UTR of Apaf-1 mRNA, and luciferase results showed that miR-27b-3p had a targeted relationship with Apaf-1. : The miR-27b-3p target inhibits the expression of Apaf-1, reduces the level of endothelial cell apoptosis, and interferes with the therapeutic effect of propranolol.