Abstract: Marine risers are the key components for transporting offshore oil and gas to production platforms, experiencing the potential risk of two-phase flow-induced vibration. Based on the established gas-liquid two-phase flow loop, the hydrodynamic slug-flow-induced vibration of a hybrid riser was experimentally investigated at different gas-liquid ratios. The non-intrusive measurement with high-speed cameras was employed to capture the response displacements as well as the internal two-phase flow. The experimental results indicate that the in-plane response amplitude and the length of the liquid slug increase with the gas-liquid ratio. Moreover, the mode switching becomes more frequent. The dominant vibration frequency of the flexible jumper coincides with the recurrence frequency of long liquid slug and the fluctuation frequency of pressure. The oscillation frequency of the rigid riser is observed in the vibration of the flexible jumper, but its influence is continuously attenuated along the jumper axis. Furthermore, the influence is weakened with the increase of gas-liquid ratio.