Abstract: The structure and beam propagation property of helical axicon is analyzed. Based on diffraction integral theory, propagation process behind helical axiocn incident by diverging spherical wave and Laguerre-Gauss beam is studied. The result shows that Bessel beam is generated by helical axicon after diverging spherical wave incident, its beam order is equal to topological charge, but central spot (hollow spot) radius increases with propagation distance; Bessel beam is also generated by helical axicon after Laguerre-Gauss beam incident, but its beam order is equal to the sum of topological charge of Laguerre-Gauss beam and helical axicon, and the topological charge of the outgoing beam is equal to beam order itself.