A cooling tower includes a tower casing, a pumping device, a water storage tank, at least one cooling assembly and a fan unit. The cooling assembly includes a first multiple-layer cooling unit comprising a first water collection basin, a first fill material unit provided underneath the first water collection basin, and a first water receiving basin provided underneath the first fill material unit and connected to the water storage tank. The second multiple-layer cooling unit includes a second water collection basin connected to the water storage tank, and a second fill material unit provided underneath the second water collection basin. The cooling water in the second water collection basin is arranged to be distributed on the second fill material unit. The water flowing in the second water collection basin is collected in the water storage tank.