<p>The vortex-induced vibration (VIV) characteristics of a long-span twin continuous steel box girder bridge under varying wind angles of attack (<i>α</i>_<i>m</i>), Scruton numbers (<i>Sc</i>), heights of beam (<i>D</i> = 0.078 m, 0.108 m, and 0.137 m) and layout forms (twin, single, and twin-girder fixed) are comprehensively investigated by sectional model wind tunnel tests with a scale ratio of 1:40. Results indicate that the VIV response of twin-box bridge is highly complex and shows no clear trend with changes in <i>D</i> or <i>α</i>_<i>m</i>. Specifically, the <i>D</i> = 0.078 m model achieves the strongest VIV at <i>αₘ</i> = 5° with the downstream girder having significantly higher maximum dimensionless amplitude (<i>Aₘₐₓ/D</i>) than the upstream one; the <i>D</i> = 0.108 m and <i>D</i> = 0.137 m models reach maximum vibration at <i>αₘ</i> = -5°, where the downstream girder has higher amplitude except for a slight upstream advantage in the <i>D</i>=0.108 m model. The phase difference between upstream and downstream bridge is minimal at the onset of the lock-in region, increases toward approximately 180° as wind speed rises, then gradually decreases. Increasing <i>Sc</i> leads to reduced <i>A</i>_<i>max</i><i>/D</i>. Under different layout forms, the largest <i>A</i>_<i>max</i><i>/D</i> occur in the twin, single and twin-girder fixed models at <i>α</i>_<i>m</i> = +3°, 0° and –3°, respectively</p>