The present invention belongs to power generation field. It relates to a method for improving cooling capacity of a power station direct air-cooling system and the cooling system thereof. According to the present invention, a transformer in a cooling system is connected to a voltage of the power grid and outputs a voltage to an electric motor, so that its working voltage reaches 380-390V; a frequency of 40-47 HZ is output from a frequency converter in the cooling system to the electric motor; a fan is driven by the electric motor working under 380-390V and 40-47 HZ to rotate according to a set velocity ratio with the aid of a speed reducer, and cooling wind is delivered by the rotating fan head-on to a heat radiator. The present invention can be widely applied in rebuilding of existing direct air-cooling units, or designing of new power station direct air-cooling systems.