The invention discloses a controller. The controller comprises a sealed controller housing, joints, water nozzles, a bus-bar, a capacitor, a power module, and a radiator; the sealed controller housingis composed of a shell, a cover plate A and a cover plate B which are respectively arranged at the left end and right end of the shell; the joints and the water nozzles are arranged on the cover plate A and the cover plate B; the bus-bar, the capacitor, the power module, and the radiator are arranged in the controller housing; the capacitor, the power module and the joints are connected with oneanother through the bus-bar; the radiator is of a hollow water-cooled structure; the water nozzles are used for water inflow and outflow of the internal water pipeline of the radiator; the capacitor is disposed in the hollow portion of the radiator; and the power module is disposed on the radiator. With the controller of the invention adopted, the technical problems of large size, complicated structure, poor maintainability, and large occupied space of an existing converter can be solved.