The invention relates to a method for reducing reserved width of waterproof coal pillars of an inclined coal seam. The work plane employs external-staggered layer-staggered type tunnel layout, the air intake tunnel of the work plane is arranged along the top board of the coal seam, and the air return tunnel is arranged along the bottom board of the coal seam; the angle of the working plane is gradually uplifted to approximate horizontal from downward incline before the work plane approaches the air intake tunnel, and also the exploitation thickness of the work plane is gradually reduced to the height of the air intake tunnel, so that the problem that the reserved width of conventional waterproof coal pillars is too large; and under the prerequisite that adjacent goaves are prevented from water-bursting, the method helps to reduce the reserved width of the waterproof coal pillars and improve recovery rate.