Based on Hugens-Fresnel diffraction integral theory, the propagation formula of an optical bottle beam generated by an axicon-lens system was deduced. The three-dimensional (3D) and cross-section optical intensity distribution were simulated. Using the diffraction integral theory and geometry method, the influence of the focal length of the lens on the sizes of the bottle beam was analyzed in detail. The results show that the sizes of the bottle beam (including the bottle radius and bottle length) increase with the increase of the focal length of the lens under the same condition. In the experiment, the bottle radii of 200 μm, 300 μm and 430 μm are obtained with the focal length of 50 mm, 70 mm and 100 mm respectively. The result fits well with theoretical calculation and numerical simulation.