Step refractive index axicon for generating bottle beam is proposed for the first time, and the two kinds of models-refractive index step-increase or decrease in radial direction are discussed. The principle of the bottle beam generation is analyzed by geometrical optics. The optical field distribution and 2D light spot image at different propagation distance behind the two kinds of axicons are numerically simulated using the diffraction integral theory. Research result shows that the step-decrease refractive index axicon generates single bottle beam, and the step-increase refractive index axicon generates periodic bottle beams. Bottle beam has a wild application in atom guiding and trapping,optical capture and optical tweezers. Research results in this paper give the significant guidance for the practical applications of the bottle beam.