Abstract: Based on an annular shaped charge with aluminum liner, different modes of initiation (initiation radius D₁) and length-to-diameter ratio (L/D) were simulated by Autodyn to measure the formation and jet speed of the annular jet. Numerical results showed that the formation process of the annular jet was mainly influenced by L/D, the jet tip had an inward deflection when L/D was relatively small, and an outward deflection otherwise. The axial jet speed was positively related to and also mainly influenced by L/D, and the maximum difference was about 700 m/s. The radial jet speed was mainly influenced by modes of initiation, and the maximum radial jet speed difference was about 220 m/s. The radial jet speed gradient was greater when D₁ or L/D was relatively small or big. Combined with jet formation and speed, D₁=0.5D and L/D=1.0 were preferred settings for this charge. The hole diameter of the concrete target was 2.6D₁, which is 7.7% bigger than the numerical result. The penetration experiment demonstrates that the calculation model and method are appropriate.