Abstract: In order to investigate the effect of pH-responsive hydrogel indicator film on the preservation and freshness indication of fruits and vegetables, the hydrogel film was prepared by using sodium alginate and gelatin as the substrate, and glycerol as the plasticizer, and the response surface was optimized by taking the mechanical properties and the water vapor transmission rate as the test indexes; acylated anthocyanin and alizarin were compounded as the indicators, and the structural characterization and the performance of the hydrogel films with different indicator additions were determined, so that the prepared hydrogel films with better performance could be selected for blueberry preservation and freshness monitoring and freshness indication. Through the structural characterization and performance determination of different indicator additives, the hydrogel indicator film with better performance was selected to be prepared for blueberry preservation and freshness monitoring and preservation. The results showed that the hydrogel indicator film prepared under the conditions of 3.108% sodium alginate, 1.587% gelatin, 3.176% glycerol and 15% indicator addition had relatively strong and excellent basic properties, swelling properties, microscopic morphology and structure, degree of crystallinity, thermal stability, antioxidant properties and color temperature stability, and had a good color response at pH 2-12. The color response was good in pH 2~12. During the storage period of blueberries (0~18d), the hydrogel indicator film has good freshness preservation effect, which can delay the corruption and deterioration of blueberries. When blueberries are fresh, the hydrogel indicator film is purple; when blueberries are inedible, the hydrogel indicator film is orange. The hydrogel indicator film has good application prospects in fruit and vegetable preservation and freshness indication and fruit and vegetable preservation.