To comprehensively understand the characteristics and patterns of projectile penetration behavior and provide theoretical support and experimental evidence for projectile design, optimization, and engineering applications, this study investigates the penetration process of 4 mm and 5 mm diameter tungsten alloy spherical projectiles into gelatin. High-speed photography was used to measure data such as cavity diameter, projectile penetration depth, and the gelatin elastic wave profile. This study identified four typical cavity morphologies during the penetration process that appeared successively with increasing penetration depth. The instantaneous cavity “expansion-contraction” cycle differs between projectiles of the two sizes, with larger projectile diameters exhibiting longer “expansion-contraction” periods. “Cylindrical” cavities appear when the velocities of the 4 mm and 5 mm projectiles decrease to 68 m/s and 85 m/s respectively. Additionally, the expansion size and velocity of the gelatin elastic wave were quantitatively analyzed, providing a theoretical basis for understanding the dynamic response of gelatin cavities. These research findings not only contribute to a deeper understanding of the behavioral mechanism of tungsten alloy spherical projectile penetration into gelatin but also have significant reference value for assessing the lethality of projectiles against living targets, providing strong support for research and applications in related fields.