In this paper a gas mixing device and an instrument for measuringthe permeability of gases in plastic film for modified atmospheric packaging foods wereengineered. The component gases were charged into the mixing device at a given ratioby controlling the partial pressures of two or three component gases. The device wasincorporated with a conventional vacuum packaging machine used for the modifiedatmospheric packaging. The gas permeability instrument was used to measure thepermeability of individual gas in plastic film so as to properly select packaging mate-rial to be used. In this experiment jelly fish was packaged in three different kinds of plastic filmpouches into which various proportions of CO_2/N_2 gas mixture were admitted. Thenthe pouches were sealed and stored under different temperatures in order to attain theoptimum factors influencing the keeping quality of the item. The results show that alonger shelf life of jelly fish packages in plastic film pouch of low permeability and inthe modified atmosphere even stored at ordinary temperature was obtained in case theinitial bacteria counts in the raw material was low and the proportion of CO_2/N_2 gasmixture was properly selected.