The invention provides a method for analyzing the influence of plume of a cooling tower on nuclear waste gas concentration distribution on a nuclear island. The method comprises the following steps of: building a calculation domain according to relative positions and geometric sizes of the cooling tower and a high-altitude chimney on the nuclear island; building a calculation grid of a calculation domain; in the calculation domain, presetting environment wind speed and turbulent intensity at different heights; acquiring nuclide decay source items; building a three-dimensional turbulent transportation model in the calculation domain; setting a boundary condition of the calculation domain; solving the three-dimensional turbulent transportation model according to the preset environment wind speed and the preset turbulent intensity at different heights, the nuclide decay source items and the boundary condition, and obtaining nuclear waste gas diffusion concentrations on the nuclear island at different space positions and different moments; and when the nuclear waste gas diffusion concentration is greater than a preset concentration value, reducing the nuclear waste gas discharging speed of the high-altitude chimney on the nuclear island. Compared with the conventional method, the diffusion situation of the nuclear waste gas around the nuclear island can be accurately reflected; and the air quality around the nuclear island can be guaranteed.