The invention discloses a vacuum brazing tool for a water-cooling plate. The vacuum brazing tool comprises a movable trolley, wherein a clamping device is arranged on the movable trolley and comprises a bottom board, a cover plate and at least one group of clamping device, wherein the bottom board and the cover plate are vertically superposed; and the vacuum brazing tool is characterized by further comprising a C-shaped main frame, wherein a suspension beam is arranged on the upper part of the C-shaped main frame, a vertical moving device which can move along the direction of the suspension beam is arranged on the lower side of the suspension beam, a pressing block is arranged on the bottom end of the vertical moving device, and at least one load sensor is arranged on the bottom of the pressing block. According to the tool, total press fitting force on the water-cooling plate can be accurately controlled, the press fitting force on each part of the water-cooling plate is basically consistent, and thus, the deformation of each clamp is slight and consistent, the service life of each clamp is prolonged, round hole structures of parts such as the bottom board and a pressing board are beneficial to the internal radiation heat adsorption and heat dissipation of a product in a vacuum brazing furnace, so that the brazing efficiency is improved, after the tool is adopted to weld the water-cooling plate, the once finished product rate can reach above 90%, and the tool can be widely applied to the assembling of the water-cooling plate before the vacuum brazing.