This study aimed to examine the vibration characteristics of EPE and use it as a reference index for packaging vibration-isolation design. The paper built an EPE viscoelastic mathematic model, and then a nonlinear packaging model with two degree of freedom containing a critical component based on quarter transport vehicle. The vibration characteristics coupling the linear elastic critical component and viscoelastic EPE was studied. The effects of area and thickness of an EPE cushion above the damaged boundary on the acceleration distribution were discussed. The results showed that the acceleration response of the critical component was influenced by the area and the thickness of EPE cushion. With increasing area and thickness of EPE cushion, the acceleration decreased firstly, and then fluctuated within a small range. In conclusion, the economy and safety concepts were proposed to comprehensively evaluate the vibration-isolation design, and the parameter λ was introduced to characterize the economical efficiency of the EPE cushion and the safety of the critical component.