To keep GIS (Gas Insulated Substations) bus bar device safe from long distance transportation, EVA (ethylene–vinyl acetate copolymer) plastic support is used as buffer. Creep caused by long-term pressure during ocean carriage should be taken into consideration to avoid structural damage. This paper develops a process to combines the FEA (finite element analysis) result calculated by ABAQUS and numerical iteration to predict the large creep deflection of the EVA plastic support. Result shows that the theory can predict a more accurate process of creep behavior and a purely numerical guide is built for assessment at packaging site.