The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena. The dynamic expansion of the cavity induces liquid pressure variations, potentially causing catastrophic damage to the container. Current studies mainly focus on non-deforming projectiles, such as fragments, with limited exploration of shaped charge jets. In this paper, a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts. The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE) solver. The formation mechanism, along with the dimensional and shape evolution of the cavity was investigated. Additionally, the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed. The findings reveal that the cavity profile exhibits a conical shape, primarily driven by direct jet impact and inertial effects. The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy. When the impact kinetic energy is reduced to 28.2 k J or below, the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7.