To investigate the influence of torpedo guidance nose configuration on the lethality of an underwater shaped charge warhead, a series of numerical simulations were performed using the AUTODYN finite element code. The damage performance of the shaped penetrator under different simulated nose structures was studied, and the complete process including shock wave diffraction, behind-target load propagation, and target damage were analyzed. The results indicate that both the penetrator head velocity and the diameter of hole in after-effect target generally increase with the total length and number of layers of the simulated nose. Within a certain range, increasing the number of nose layers effectively optimizes the formation of the explosively formed projectile (EFP), thereby enhancing its penetration capability. Furthermore, there exists an optimal total nose length that maximizes the head velocity while preventing necking and fracture of the penetrator.