Abstract: Using the non-diffracting beam along the axes z,a spatial straight line can be reasonably obtained.Furthermore,the non-diffracting beam has better tolerance properties to the drift of laser beam than that of the common collimated laser beam and its optic axes is more stable than the enlarged laser beam.So it is more suitable to be used as the spatial datum-line for straightness error or coaxiality error measurement.Based on the non-diffracting beam datum-line and combining roundness measuring technology with its amending technology,a high precision coaxial measurement method for a hole has been proposed in this paper.The principle of the measuring system is introduced and theoretical error analysis and test are made to verify it.