The invention discloses a heat-dissipation device for an electric vehicle controller. The heat-dissipation device comprises a heat-dissipation top board and a seal cover plate installed on the top of the electric vehicle controller, and the heat-dissipation top board is installed on the top surface of the seal cover plate; one side, on the top surface of the seal cover plate, provided with the heat-dissipation top board is provided with a refrigerant chamber, the other side on the top surface of the seal cover plate is provided with a diffusion chamber, and the heat-dissipation top board is provided with several capillary siphon channels which can connect the refrigerant chamber with the diffusion chamber; the refrigerant chamber comprises a first cavity arranged on the top surface of the heat-dissipation top board and a second cavity arranged outside the top surface of the heat-dissipation top board; the second cavity contains liquid refrigerant; the first cavity is connected with the diffusion chamber through a return pipe; a barrier plate is arranged between the first cavity and the second cavity, and the barrier plate is provided with several air vents. According to the invention, the spatial structure characteristic of the electric vehicle is fully combined, under the condition that the heat-dissipation effect of the controller is improved, the heat-dissipation device does not occupy the installation space of the controller, the performance of the controller is finally improved, and the heat-dissipation device is suitable for being promoted.