Abstract: In the present study, sodium alginate-based intelligent cross-linked films were prepared using cinnamon essential oil (CEO, 2.0wt%) as the antibacterial component and vacuum-freeze-dried purple sweet potato anthocyanin (PSPA) at concentrations of 0%, 0.2%, 0.6%, 1.0%, 1.4%, and 1.8% w/v as the indicator. The effects of PSPA addition on the film properties (including dissolution, barrier, optical, and antibacterial performances) as well as the response to ammonia compounds and pH were tested. In addition, the effect of the films on real-time monitoring of shrimp freshness was evaluated. The addition of CEO and PSPA endowed the films with notable growth inhibitory effects against Escherichia coli and Staphylococcus aureus. The films containing PSPA had greater thickness, water vapor permeability, and oxygen permeability than the control films, whereas the water solubility, water content, swelling ratio, and light transmittance decreased with increasing PSPA concentration. Additionally, incorporation of PSPA enhanced the ultraviolet barrier performance of the films and resulted in clear color responses to concentrated ammonia water, dimethylamine, trimethylamine, and pH1~13 buffer solutions. The results of the shrimp freshness monitoring test indicated that the SA-based films containing PSPA exhibited good color indication effects on the volatile nitrogen-containing compounds produced during the refrigeration process of shrimp and could be used to effectively monitor the changes in freshness of shrimp in real time. Moreover, under the synergistic effect of CEO, the pH, thiobarbituric acid reactive substances (TBARS), volatile basic nitrogen (TVB-N), and total bacterial count (TVC) of shrimp samples during storage were reduced, and the shelf life of shrimp was prolonged. These results indicate that the developed film has significant potential as a packaging material for nondestructive monitoring of the freshness of aquatic products.