The utility model discloses an underwater high-speed object generator produced along with a super-cavity, which comprises a high-pressure gas source, a box support frame, a high-speed photographic apparatus, an industrial control computer, a diaphragm, a safety interceptor, a water tank, a water tank cover, a flat plate, a ball valve, a shooting tube, a strengthening plate, a gas guide pipe, a fastening plate and a shooting tube support frame. An object to be tested is driven by nitrogen or helium released by the high-pressure gas source to increase the speed and is then shot into the water tank with liquid through the shooting tube. When the object to be tested passes through the free surface of the liquid from top to bottom and from bottom to top, a water inlet flow field and a water outlet flow field can be produced along with the super-cavity. The super-cavity has a relatively clear internal and external border for steam-liquid phase flow, and various optical instruments and flow field visualization instruments can be used together with the generator for study and understanding of the gas balance in the cavity, interaction of the free surface and the super-cavity, instability of the steam-liquid interface, development of the turbulent boundary layer and other complex behaviors of fluid dynamics.