The invention discloses a sea test device for monitoring vortex-induced vibration. The device comprises a test ship, test stand pipes, a vortex-induced vibration suppression device, underwater movement monitors, a dragging frame, a traction cable, a weight balancing block, a traction guiding support, a supporting rod and a triangle connection plate. Top ends of one test stand pipe with the vortex-induced vibration suppression device and one test stand pipe without the vortex-induced vibration suppression device are hinged with the dragging frame, the two test stand pipes are fixed at the position of a stern through the dragging frame, the underwater movement monitors are installed on the two test stand pipes respectively for monitoring and recording dynamic responses of the test stand pipes in the process of a test, states of the stand pipes after the stand pipes suffer from ocean current speeds can be simulated by adjusting ship speeds, the underwater movement monitors installed on the test stand pipes can be real-timely monitored, and motion response data of the test stand pipes can be recorded. Collected data are compared and analyzed to finally obtain validity of the vortex-induced vibration suppression device.