A model of three-beam interference has been set up to explain the observed beam patterns which are generated by Gaussian beam passing through an axicon. The mathematical simulation is based on interferential theory,and the effect of the vertex of the axicon. is also considered. The derived equation for describing the transverse intensity distribution gives good approximation to the experimental result as well as the zero-order Bessel function. This beam is characteristic of non-diffraction and can be used to study the newly-type optical tweezers.