The invention discloses a machine tool guide track with a pretightening device and a pretightening method for the machine tool guide track. The machine tool guide track comprises a slide carriage, a linear bearing, a bearing pressing strip, a bearing wedge and a guide track, wherein the slide carriage is slidably connected to the upper portion of the guide track; a projection which extends downwards is arranged on the bottom of the slide carriage and is in sliding contact with a side surface of the guide track; the linear bearing, the bearing pressing strip and the bearing wedge are arranged below the slide carriage; one end of the bearing pressing strip is fixed on the bottom surface of the slide carriage; the other end of the bearing pressing strip is provided with an adjusting flat plate; the adjusting flat plate is provided with a bearing wedge positioning device; the bearing pressing strip is provided with a pressing strip inclined surface; the bearing wedge is provided with a wedge inclined surface of which the inclination is consistent to that of an inclined surface of the pressing strip; the wedge inclined surface is in sliding contact with the pressing strip inclined surface; and the linear bearing is fixed on the bearing wedge and is in rolling contact with a side surface, which is far away from the projection, of the guide track. The magnitude of a pretightening force of the machine tool guide track with the pretightening device can be adjusted at any time.