Objective To investigate the vasodilatory effect of luteolin on isolated denuded-endothelium rat thoracic aorta (DRTA) vascular rings, and the mechanistic role of the Kv7 ion channel. Methods The tension of DRTA vascular rings was measured using an ex vivo tissue perfusion muscle-tone detection system. DRTA vascular rings were pre-contracted with 60 mmol/L KCl or 0.3 μmol/L U46619, and the effect of luteolin on vascular-ring relaxation was observed at 1, 3, 10, 30, 100 and 300 μmol/L. The effects of 4-AP, XE-991, and ML213 on luteolin-induced vasodilation were also observed. The effect of luteolin on KCNQ1-KCNQ5 expression in the thoracic aorta was detected by real-time fluorescence quantitative polymerase chain reaction. Expression levels of Kv7.1 and Kv7.4 proteins in the DRTA were detected by Western blot. Results (1)The luteolin-induced maximum vasodilation rates in DRTA pre-contracted with 60 mmol/L KCl and 0.3 μmol/L U46619 were (97.67±8.51)% and (98.42±9.76)%, respectively. The vasodilation effect was concentration-dependent (P<0.05). (2)4-AP (3 mmol/L) significantly reduced the vasodilatory effect of luteolin on DRTA vascular rings at 10, 30, and 100 μmol/L (P<0.05), and XE-991 (3 μmol/L) significantly reduced the effect of luteolin at 30 and 100 μmol/L (P<0.05), while ML213 (1 μmol/L) significantly enhanced the vasodilatory effect of luteolin at 3, 10, and 30 μmol/L (P<0.05). (3)The relative gene expression levels of each subtype of Kv7 channel in normal DRTA were KCNQ1 > KCNQ5 > KCNQ4 > KCNQ3 > KCNQ2, with KCNQ1 being the most highly expressed. (4)Luteolin significantly enhanced the expression levels of KCNQ1 at 3, 10, 30, and 100 μmol/L, KCNQ2 at 1, 3, 10, 30, and 100 μmol/ L (P<0.05), KCNQ3 at 3, 10, 30, and 100 μmol/L, and KCNQ4 at 10, 30, and 100 μmol/L (P<0.05), but did not significantly enhance the expression of KCNQ5 at 1, 3, 10, 30, or 100 μmol/L (P>.05). (5)Luteolin significantly increased the expression of Kv7.1 protein in DRTA at 3, 10, 30, and 100 μmol/L (P<0.05) and the expression of Kv7.4 at 10, 30, and 100 μmol/L (P<0.05). Conclusions Luteolin-induced dilation of DRTA vascular rings may be related to the enhanced gene expression of KCNQ1-4 and increased expression of Kv7.1 and Kv7.4 channel proteins.