Simple expressions based on the method of stationary-phase are derived for the axis line images produced by acicons illuminated by spherical wave. By using these expressions, the characteristics of its energy flow along axis and the lateral intensity distribution are gotten. The numerical calculations indicate that the on –axis intensity distribution and focal depth range can be developed and the lateral intensity distribution may be ensured by choosing correct spherical wave. For the axicons with 20 mm radius, 10 -2 cone angle, when using incident spherical wave whose radius of curvature varius from 1200 mm to 1400 mm, the focal length increases from 200 mm to 120 mm and the lateral intensity distribution increases only 15μm.