Abstract: Integrated with related penetrating test results and mesoscopic finite element simulation analysis, the deformation and failure characteristics of tungsten fiber reinforced metallic glass matrix (WF/MG) composite long rods with different fiber diameters were investigated systematically, and the similarities and differences among the ‘self-sharpening’ behavior as well as the corresponding penetration / perforation performance of various composite long rods were discussed, then the transformation of deformation and failure modes of projectiles under different impact velocities was analyzed in detail. Related analysis demonstrated that due to the differences in the mechanical properties among the tungsten fibers with different diameters, i.e., bending resistance and shear resistance, etc., the corresponding composite long rods exhibit different failure characteristics during the penetration process, and it further affects their penetration / perforation performance. The impact velocity also plays an important role on the deformation and failure modes of composite long rods and the corresponding penetration / perforation performance: when the impact velocity is relatively low, the fibers in the nose of composite rod projectile exhibits unstable buckling phenomenon and gradually disperse during the penetration process, which makes the projectile nose blunt at a certain extent, and induces the increase in the penetration resistance and decrease in the penetration performance; along with the impact velocity increases, in the case that the fiber diameter is small, the fibers on the outer side of projectile nose refluxes back, and when the fiber diameter is large, the fibers mainly behave as shear failure, and it further strengthen the ‘self-sharpening’ behavior as well as the penetration performance of projectile; when the impact velocity and fiber diameter reach a certain upper threshold values, The thickness of ‘edge layer’ in the rod nose is sharply reduced, and thus the ‘self-sharpening’ property is weakened, and the penetration performance of projectile is decayed again. Related research is beneficial to predicting the penetration / perforation performance of WF/MG composite long rods with different fiber diameters under different impact velocities, and optimizing the structural design of projectile as well as the impact velocity, etc.