To study the influence of flat top size and initiation ring radius of composite liner on jet head velocity and forming, numerical simulation of copper-aluminum composite liner with different flat top size and initiation ring radius was carried out. Use AUTODYN-2D to simulate the deformation of composite liner and the formation and fracture process of the jet, simulate the effect of the flat top size on the jet, the influence of initiation ring size on jet formation, the influence of flat top size and initiation ring radius on jet forming were simulated, and the situation of liner crushing inner liner was analyzed. The results show that when the detonating ring radius is small, the top size of composite liner is smaller, and the jet head velocity is higher; when the detonating ring radius is large, the larger top size can obtain a higher jet head velocity. When the charge diameter is increased to about 20%, the inner cover may break the outer liner during forming.