Abstract: The highly mature ‘Xianju bayberry’ by cold chain transportation was selected as the experimental material. In view of the high-water content and high respiratory intensity of bayberry fruits, a spontaneous modified atmosphere packaging bag made of film with selective permeability to water vapor was used for packing,then the relevant indices of postharvest qualities were determined regularly. The effects of headspace gas volume fractions on the qualities of bayberry fruits at ambient temperature of（26±1） ℃ were explored, so as to judge the fresh-keeping effects of the spontaneous modified atmosphere packaging bag on bayberry fruits. The results showed that the volume fractions of oxygen, carbon dioxide, relative humidity maintained by spontaneous modified atmosphere package were 13%±3%, 8%±1%, and 95%±1%. These conditions could effectively reduce the nutrients loss and bad fruit rates, slow down the decline of hardness, and effectively prolong the shelf life of fresh bayberry fruits.