The present invention discloses a device and method of realizing a complex flow field of an aquatic organism ecohydraulics experiment. An experimental device is an annular water tank and is formed byconnecting a first arc-shaped water tank, a first heteromorphic water tank, a second arc-shaped water tank and a second heteromorphic water tank end to end orderly, wherein the inner walls of the first heteromorphic water tank and the second heteromorphic water tank are both planes, and the width between the outer wall and the inner wall is increased gradually from the two ends to the middle; a first baffle is arranged in the first heteromorphic water tank along a length direction, a second baffle is arranged in the second heteromorphic water tank along the length direction, and the flow propellers and the submersible pumps are also arranged in the heteromorphic water tanks. The realization method of the present invention adopts the different combinations of the flow propellers and the submersible pumps to realize different maximum flow velocities, and the experimental device of the present invention can realize the complex flow field, is more suitable for the parent fish oviposition research.