The invention discloses a detection tool and method for measuring the axial position size of a semicircular key slot of a bent shaft. The detection tool comprises a
gauge block and a measure gauge, wherein the
gauge block is of a flat round shape, the thickness of the
gauge block is designed according to the width of the key slot, the round
diameter of the gauge block is designed according to the
diameter of the inner arc of the key slot, when the gauge block is put into the key slot, an arc of the gauge block is in contact with two sides of the inner arc of the key slot to realize V-shaped positioning, and a
central line of the gauge block in the vertical direction overlaps a
central line of the inner arc of the key slot; and the measure gauge is a cylinder with a through end and a stop end, the diameters of the through end and the stop end are determined according to the outer diameters of the semicircular key slot, a measurement
reference surface and the gauge block, and the gauge block and the measure gauge are matched in use so as to determine whether the size of a detected component from the center of the semicircular key slot to the
reference surface meets the drawing requirements. When the technical scheme of the invention is used for measuring the axial position size of the semicircular key slot of the bent shaft, the
measurement cost is low, the measurement accuracy is high, an operation method is simple, and the detection efficiency is high.