The invention discloses an automatic grinding machine for metallographic specimens, which comprises a basal body, an automatic adjusting stand, a spray pipe, a swivel bearing, a driving motor, a driving gear, a driven gear, a rotating disk and a sandpaper pad, wherein the swivel bearing is fixedly mounted on the basal body, the driven gear is fixedly mounted on the swivel bearing, the driven gear is engaged with the driving gear mounted on a spindle of the driving motor, and the driving motor is fixedly mounted at the back side position of the basal body. The rotating disk is fixedly mounted at the upper part of the driven gear, and the sandpaper pad is fixedly mounted above the rotating disk. The automatic adjusting stand is vertically mounted at the upper part of the basal body, adjustable pressing rods are arranged on a crossbeam of the automatic adjusting stand, and adjustable pressing blocks are mounted at the lower parts of the adjustable pressing rods. The spray pipe is fixedly mounted on the basal body. By arranging the multi-layer annular sandpaper pad and the adjustable pressing blocks, the working efficiency of the automatic grinding machine is increased, and moreover, the pressure between a metallographic specimen and sandpaper can be flexibly adjusted to meet different grinding requirements; the structure of the automatic grinding machine for metallographic specimens is simple, the design is reasonable, and the cost is low.