The invention relates to a double-runner water turbine for a cooling tower and with spherical spiral blades. The double-runner water turbine comprises a spiral case 1, a gate operating mechanism 2, a base runner 3, a water outlet pipe 7, a supporting plate 8, a main shaft 9, a bearing assembly 10 and a fan 11. The double-runner water turbine is characterized by also comprising an energy increasing runner 4, and the energy increasing runner 4 is located below a water outlet of the base runner 3 and is connected with the base runner 3 through a flange; and the energy increasing runner 4 comprises the spherical spiral blades 5 and a conical circular pipe 6, wherein the spherical spiral blades 5 are axially and gradually stretched in the axial direction of the main shaft 9 according to a spherical spiral line to form a spatial cross distortion shape and are uniformly distributed on the inner wall in the circumferential direction of the conical circular pipe 6, and a coordinate system is established by taking the intersection point of the sections of the spherical spiral blades 5 taking the main shaft 9 as a central rotating surface as the original point. By using the double-runner water turbine, the purpose that water flow energy cannot be converted many times can be achieved, so that the water flow energy can be efficiently utilized, and the cooling effect of the cooling tower is improved.