The invention provides a gantry type vertical mill high-precision three-shaft grinding machine comprises a grinding machine cabinet, double supporting stand columns, a transverse beam, an X-axis lead screw transmission mechanism, an X-axis sliding base, a Z-axis sliding base, a Z-axis lead screw transmission mechanism and a grinding head main shaft; a V-shaped guide rail is arranged on the grinding machine cabinet, a working table is erected on the V-shaped guide rail, and a V-shaped sliding block is arranged at the bottom of the working table to be matched with the V-shaped guide rail; hydraulic rod supports are arranged on the front and back of the working table, a hydraulic cylinder is arranged below the working table, and the two ends of a hydraulic rod in the hydraulic cylinder are connected with the two hydraulic rod supports; and a dustproof cover plate is fixed to the outer side of the V-shaped sliding block. According to the gantry type vertical mill high-precision three-shaft grinding machine, the grinding head is arranged to be vertical, the transmission manner of the grinding machine is set to be X-Z two-axis transmission, and special workpieces can be machined; the manner of lead screws and sliding blocks is adopted, and the positioning accuracy of the grinding head is greatly improved; and the working table transmitted through the Y axis is adopted, and therefore machining through the vertical grinding head is more three-dimensional.