The effects of PVA films containing different amount of sodium dehydroacetate on cake shelf life were studied to identify the most suitable modified packaging films for preserving cakes. The PVA active films modified with different mass fraction of sodium dehydroacetate were prepared by casting method. The cake was cut into certain sizes and put into different PVA film packaging bags for storage test. The sensory evaluation of the cake was made every three days on the weight loss rate, the total bacterial count, acid value, peroxide value to evaluate the antibacterial and antioxidant effect of the modified packaging. The results showed that the preservation effects of modified PVA films with sodium dehydroacetate were better than that of unmodified PVA film; a favorable fresh-keeping effect was achieved by modified PVA film with mass fraction of 2% sodium dehydroacetate after summarizing all influencing factors as the loss of moisture in the cake could be effectively prevented with the strongest antioxidant performance.