A cooling system for a generator of a vehicle has an engine, a generator and a wind collection box. The generator has a rotor driven by the engine and a fan synchronously rotating with the rotor. The wind collection box is connected to the generator via a first guiding tube. The fan draws exterior air from the wind collection box and the first guiding tube to allow the exterior air to flow through the generator. Thus, heat in the generator that is mounted in an airtight engine compartment is dissipated.