Abstract: To investigate the penetration mechanism and performance optimization of D-shaped cross-section projectiles into ultra-high performance concrete (UHPC) targets, penetration experiments were conducted using 254 g D-shaped cross-section projectiles against semi-infinite UHPC targets with initial velocities ranging from 596~836 m/s. Numerical simulations were used to analyze the influence of parameters including cross-sectional width-height ratio, nose length-equivalent diameter ratio, and length-diameter ratio on the penetration characteristics of D-shaped projectiles. The results show that under equivalent launch platform constraints, compared with conventional circular cross-section projectiles, the D-shaped projectiles achieved 8.0%~12.6% greater penetration depth with smoother acceleration changes. Increasing the length-diameter ratio could significantly enhance the penetration capability of D-shaped projectiles while reducing their acceleration variation rate. When the D-shaped cross-section width-height ratio increased from 1.0 to 1.2, the penetration depth increased by approximately 6.0%~8.5%, while this parameter showed a negligible impact on penetration depth within the 1.2~1.8 range. As the γ (nose length-equivalent diameter ratio) increased, the penetration depth showed only marginal improvement (less than 5%), indicating high design flexibility of D-shaped projectiles. These findings extend the penetration theory of asymmetric projectiles and provide technical support for the application of special-shaped warheads.