The invention relates to a twin-runner water turbine provided with Archimedes helical blades and used for a cooling tower. The twin-runner water turbine comprises a volute casing 1, a water guide mechanism 2, a base runner 3, a water outlet tube 7, a supporting plate 8, a main shaft 9, a bearing assembly 10 and a fan 11. The twin-runner water turbine is characterized by further comprising an energy-increasing runner 4 which is positioned below a water hole of the base runner 3, wherein the energy-increasing runner 4 is connected with the base runner 3 through a flange; the base runner 4 comprise the Archimedes helical blades 5 and a tapered circular tube 6; the Archimedes helical blades 5 are gradually stretched according to the axial direction, along the main shaft 9, of an Archimedes helical line to form a spatial-cross twisted shape and are uniformly distributed on the peripheral inner wall of the tapered circular tube 6; and a coordinate system is established by taking a crossed point of sections of the Archimedes helical blades 5 taking the main shaft 9 as the central rotary surface as the origin. The twin-runner water turbine can solve the multi-time energy conversion problem of water flow energy for realizing efficient utilization of water flow energy, so that the cooling effect of the cooling tower is improved.