Abstract: To realize a supply of drinking water and oil for field forces and emergent rescuers, this article reported a design and development of rotation molding technology for a water storage tank in free drop. A type of liquid storage equipment with a free-dropping and easy-carrying capability was designed and then a reasonable scheme including the structure, shape, materials and molding process design was proposed to meet the requirement of practical applications. The feasibility and reasonability of the scheme were verified by theoretical analysis and practical airdrop test. The results indicated that the structure, materials, technology and performance of the rotation-molded water storage tank in free drop met the requirement of free drop for liquid, and there is no leakage of liquid for normal use of airdrop. It is concluded that the water storage tank in free drop developed by this work is a new type of practical, convenient and economical airdrop equipment that is suitable for practical use.