Distribution packaging practices demonstrate over-package or material wastes due to the conservatism in fragility according to traditional damage boundary curve(DBC) applied in cushioning packaging design. Based on the basic features of shock response spectrum(SRS) in vibration theory, the model of Maurice Biot(Biot Model) is put forward and used as a structural model by taking the product structure as a vibration system consisting of a number of single degree of freedom(SDOF) mass-spring oscillators. Through testing and measuring by use of advanced electronic equipments with automatic signal analysis devices, the SRS of elected fragile elements in the structural system can be obtained. Then from the concept of dynamic coefficient(G factor) in engineering mechanics, the G factor is just nearly equal to the fragility Gs of the element when the maximum stress in the element dangerous point reaches the elastic limit of the element material. That means each Gs in the new DBC based on responses can be drawn graphically indicating the relationship between critical maximum response accelerations and natural frequencies of the key parts in products system. According to the new DBC, the new fragility based on response acceleration of a key part in product system can be acquired if the natural frequency of the key part is known. This new fragility is certainly more suitable to cushioning packaging designs because the conservatism factor in traditional fragility is eliminated,