The paper aims to develop a freshness indicator film based on modified roselle anthocyanins for fresh-keeping packaging of catfish and evaluate the freshness indication effect of the indicator film. With acylated modified roselle anthocyanin as the freshness indicator, polyvinyl alcohol as the coating liquid matrix, and polypropylene as the base film, the freshness indicator film was prepared to study its response to volatile ammonia; and catfish packaging test was carried out. The results showed that with the increase of the concentration of volatile ammonia, the indicator film changed from red to purple and then to green; when the catfish changed from the fresh grade to the sub-fresh grade to the rotten grade, the color of the freshness indicator film also changed, which had strong correlation with the catfish sample quality; the principal component score of the color change of the indicating film showed a significant clustering trend, corresponding to the freshness level of the sample; the TVB-N model based on partial least squares regression can effectively predict the carp TVB-N value. The freshness indicator film has the potential to detect the freshness of fish product.