Aim To explore the antagonistic effect of sesamol on endothelial cell injury induced by oxidized low density lipoprotein (ox-LDL), and elucidate its molecular mechanism of exerting antioxidant stress, inhibiting abnormal angiogenesis and blocking endothelial-to-mesenchymal transition (EndMT) through the JNK/Nrf2/HO-1 pathway. Methods Human umbilical vein endothelial cells and human aortic endothelial cells were used to establish an endothelial cell injury model induced by 75 μmol/L ox-LDL. The CCK-8 method, DCFH-DA fluorescent probe and Annexin V/PI apoptosis detection method were used to evaluate the safety of sesamol and its effects on cell viability, as well as its protective effects against oxidative stress and cell apoptosis; Matrigel tubular formation experiment, Transwell migration/invasion experiment RT-qPCR, immunofluorescence and Western blot techniques were used to detect the effects of sesamol on abnormal angiogenesis, endothelial barrier function and EndMT; time gradient Western blot, JNK inhibitor SP600125 intervention and immunofluorescence experiments were used to verify the activation and necessity of the JNK/Nrf2/HO-1 pathway. Results The oxidative stress model of endothelial cells was successfully established by stimulating with 75 μmol/L ox-LDL for 24 hours, which showed a significant increase in reactive oxygen species (ROS) levels, upregulation of inflammation/adhesion molecule expression, downregulation of endothelial nitric oxide synthase (eNOS) and vascular endothelial cadherin expression, and an increase in cell apoptosis rate (P＜0.05 or P＜0.01). Sesamol (≤ 50 μmol/L) was non-toxic to normal endothelial cells; among them, 50 μmol/L sesamol could significantly restore the decrease in cell viability induced by ox-LDL, inhibit ROS generation and cell apoptosis (P＜0.05 or P＜0.01); simultaneously, it could significantly inhibit the formation of abnormal tube braching points and cell migration, downregulate the expression of vascular endothelial growth factor/vascular endothelial growth factor receptor 2 and matrix metalloproteinase-9, upregulate the expression of zonula occludens-1, claudin-5, and VE-cadherin, and restore nitric oxide production (P＜0.05 or P＜0.01); in addition, this concentration of sesamol could reverse EndMT-related phenotypes, reduce the expression of mesenchymal markers such as α-smooth muscle actin and vimentin, and restore the expression levels of CD31 and VE-cadherin (P＜0.05 or P＜0.01). Mechanism studies showed that sesamol could time-dependently activate the expression of p-JNK, nuclear Nrf2, and downstream HO-1 (P＜0.01); the JNK inhibitor SP600125 could block the nuclear translocation of Nrf2 and inhibit the protective effect of sesamin (P＜0.01). Conclusion Sesamol can significantly antagonize the injury of vascular endothelial cells induced by ox-LDL, and its mechanism is related to the activation of JNK/Nrf2/HO-1 pathway, inhibition of oxidative stress, abnormal angiogenesis and EndMT induced by ox-LDL, which provides an important experimental basis for its use as a potential natural drug to prevent and treat atherosclerosis.