Diesel composite armor has high penetration resistance and can be used in tank vehicles to improve their protective capability and increase fuel oil storage. This study provides a theoretical calculation method to investigate the interaction between a shaped charge jet and a diesel-filled airtight structure unit. Disturbance theory can predict the part of the jet that is disturbed by diesel fuel. The lumen radius for the container was varied to study its influence on the disturbance capability. A great lumen radius is found to cause lower maximum and minimum speeds of the disturbance velocity range of the jet, as well as a narrower disturbance velocity range. The reliability of the theoretical results was validated by experiments, and the experimental data show good agreement with the theoretical results.