The invention discloses a digital radiographic testing block for linear defects of basin-type insulators. The digital radiographic testing block is of a cuboid blocky structure, with the height of 55-65mm, made of epoxy resin and alumina powder by mixing; two metal wires and a plurality of through holes penetrating the cuboid blocky structure and different in hole diameter are horizontally and parallelly arranged in a same plane 15-25mm distant from the upper surface of the cuboid blocky structure; lengths of the metal wires are not smaller than the width of the cuboid blocky structure, and the metal wires are respectively a copper wire and a steel wire 0.1mm in diameter. Minimum linear defect which can be tested by a testing system is determined by the aid of differences, in ray absorption doses, of the through holes different in hole diameter and formed in the surfaces of steps, and by means of observing minimum testable wire diameter during different distances from the linear defects, different in thickness, of the basin-type insulators at the testing position to an imaging plate, so that linear defect testing flexibility of a digital radiographic testing system is judged intuitively.