Abstract: Because of the large beam diameter and special characteristics of the non-diffracting beam produced by an axicon,the non-diffracting beam can tolerate the eccentricity of the incident laser beam's axis to the axicon.For studying the additional tolerance property to the incident light beam's deflection,adopting a kind of incident divergent sphere Gaussian wave,it is proved that the divergent sphere Gaussian wave can tolerate the eccentricity of the incident laser beam's axis through theoretical analysis and practical tests.The obtained conclusion is that the axis of the non-diffracting beam produced by an axicon is very stable and can be adopted as the datum line to measure the spatial straightness error in continuous working distance,which may be short,medium or long.