The work aims to extend the shelf life of litchi under room temperature. A composite film with a three-layer structure was prepared for sustainable release of SO2 fungicide. The composite film was heat-sealed into the fresh-keeping packaging bags, and the "Guiwei" litchi was used as the experimental object. The naked group and the market food fresh-keeping bags were used as the control group. The effect of fresh-keeping packaging bags on litchi at room temperature was studied. The changes in mass loss rate, browning index, good fruit rate, soluble solids content and titratable acid content of litchi during storage were analyzed. The litchi exposed at room temperature and wrapped in market fresh-keeping bags would become browning severely and lose its commercial value during the shelf life of 2—3 days. When the litchi was stored in self-made fresh-keeping bags with releasable SO2, on the 6th day of the shelf life, the mass loss rate was only 2.44%, the browning index was only 1.26, the contents of soluble solids and titratable acid were 18.6% and 0.18%, respectively, and the good fruit rate was still 88.33%. The fresh-keeping packaging bags with releasable SO2 can reduce water loss, inhibit browning, maintain the flavor and taste, improve the commercial value and extend the shelf life of litchi to about 6 days at room temperature.