The work aims to study the mechanical response of the liquid storage tank with ellipsoidal structure for free drop during the process of falling and hitting the ground, in order to improve the replenishment efficiency of liquid airdrop supplies. Based on the coupling Euler-Lagrange algorithm, a finite element model of ellipsoid liquid storage tank was established. The drop process of the tank with different thickness ratios of polyethylene-foam-polyethylene was simulated by ABAQUS CAE to obtain the maximum equivalent plastic strain cloud diagram and stress-time curve. The thickness ratio between different layers is closely related to the maximum plastic strain, the time of plastic strain and the strain concentration area of the storage tank. When the thickness ratio is 1∶2∶1, the time to reach the maximum plastic strain is the shortest and the probability of strain concentration at the region for handle is increased. When the thickness ratio is 1∶1∶2, the plastic strain of the tank body is relatively reduced, but the impact resistance does not reach the ideal optimized situation. When the thickness ratio is 1∶1∶2, the plastic strain is the smallest, the maximum instantaneous speed is the highest, and the property of the tank structure is the best. Based on these, a structural optimization idea is proposed. On the basis of adding a middle foam layer to reduce the weight, appropriately increasing the thickness of the outer polyethylene material or using a material with better cushioning performance can increase the buffer energy absorption of the tank wall and improve the strength of the material structure.