Based on the principle of the equivalent momentum of the corresponding elements for internal and external liners, annular shaped charge structure is proposed. The generatrix analytical equations for the external surfaces of the external liner and external charge are deduced. Experimental and numerical studies are conducted to investigate the formation and penetration process of the jet for the annular shaped charge under different initiation radiuses, and the initiation radius corresponding to the detonation wave front matched with the liner is optimized. At this radius, shaped charge can form an ideal cylindrical jet. Moreover, the diameter of the jet approximates the theoretical diameter of the jet, and has satisfactory symmetry and focus.