The invention discloses a heat dissipater on a tractor. The heat dissipater comprises a water tank, an engine oil heat dissipater, an air heat dissipater, a heat dissipation fan, a controller and a power supply, wherein the water inlet and the water outlet of the water tank communicate with a water channel in an engine; the oil inlet and the oil outlet of the engine oil heat dissipater communicate with an oil channel in a gearbox; the front surface of the water tank is connected with the back surface of the air heat dissipater; the back surface of the water tank is connected with the front surface of the engine oil heat dissipater; the back surface of the engine oil heat dissipater is arranged in a manner of facing the heat dissipation fan; the heat dissipation fan is in circuit connection with the power supply through the controller; the controller is arranged close to the junction of the water tank and the engine oil heat dissipater; the power supply is arranged below the heat dissipation fan; and the controller comprises a metal housing, an input power line, an output power line, an insulation post and a temperature-sensing sheet. The heat dissipater adopting the design is high in heat dissipation efficiency and controllability.