The invention provides a digital display gradienter and a machine tool guiding rail leveling method. The digital display gradienter comprises a gradienter and a water channel, wherein the gradienter comprises a horizontal base, a vertical guiding rail, a ball screw, a vertical sliding block, a stepping motor, a stepping motor driver, a hand-cranking wheel, a digital display grating ruler, a static wire, an indicating lamp and a working power source. The stepping motor drives the ball screw which drives the vertical sliding block to move vertically. The digital display grating ruler comprises a grating ruler, a grating ruler reading head and a grating ruler displayer. Two ends of the working power source are respectively connected with a water tank and one end of the indicating lamp, the other end of the indicating lamp is connected with the upper end of the static wire, and the lower end of the static wire is arranged corresponding to the water tank. By means of the method, three gradienters simultaneously perform leveling on a machine tool guiding rail, a first gradienter is separately fixed and provides reference coordinates of the plane, and the other two gradienters are respectively placed on a level guiding rail and a V-shaped guiding rail for dynamically testing the relative horizontal degree of the guiding rails. The digital display gradienter is high in accuracy, and leveling through the method is high in efficiency.