The work aims to develop a food grade milk freshness indication label that can be immersed in liquid so that consumers can learn the real time quality of the milk directly. With ethyl cellulose as a polymer substrate, blueberry anthocyanin as a pH sensitive dye, Tween 80 and glycerol as plasticizers, a freshness indication label was prepared. The indication label was characterized by colorimetric analysis, swelling rate, migration test, contact angle, Fourier transform infrared spectroscopy analysis, scanning electron microscopy (SEM), and then the label was used for milk freshness monitoring to explore the relationship between the total colonies and pH of the milk and the total color difference of the indication label. The results showed that when the anthocyanin content was 10% (mass fraction) that of the ethyl cellulose, the indication effect of the indication label was the best, and the ethyl cellulose and the anthocyanin made the label have better water resistance through the combination of hydrogen bonds, and can be soaked in liquid. The migration testing proved that contact with milk would not pose a safety issue. The total colonies and pH of milk were significantly correlated with the total color difference of the label. The conclusion is that an indication label with anthocyanin content of 10% (mass fraction) that of ethylcellulose appears light purple in fresh milk and pink in spoiled milk. It can be predicted that the label has good application value and development prospects in indication of milk freshness.