An indicator showing freshness of pork via discoloration was developed. Bromocresol purple ethanol solution with 0. 2% , 0. 3% , 0. 4% , and 0. 5% concentration was mixed with 0. 7% hydroxypropyl methyl cellulose solution for preparing thin film by tape costing. Four kinds of indicator were made by putting thin film on the white waterproof paper. Indicators were packed with pork (50, 100, 150 g / tray) in the same tray wrapped with PE film to indicate freshness of the pork via discoloration during storage. TVB-N content of pork and the corresponding Lab values of indicators were determined. △E value of the indicators was calculated. The influence of bromocresol purple content on the sensitivity of the indicators was discussed. The results showed that △E value of the indicators and TVB-N content of pork was linear correlation very well; when the pork starts to be spoilage, the indicator with 0. 5% bromocresol purple is discoloration from yellow to green, and the color changing point is obvious; afterwards spoilage of the pork continue,and the indicator's color changes into blue; the discoloration of the indicator in not influenced by weight of the pork;the indicator is effective for indicating the freshness of packed pork.