A radiator includes a heat transfer base (30), a heat dissipation member (20) secured to the heat transfer base and a fan (50) mounted to the heat dissipation member. The heat dissipation member comprises a plurality of fins (22) for dissipation heat. Air guide structures are formed between the fins for guiding air from the fan to a middle portion of the heat transfer base and a middle bottom portion of the heat dissipation member in order to enhance heat dissipating efficiency of the radiator.