The work aims to study one natural indication label used for daily life with anthocyanins as the freshness indicator. The indication label was made by different pigments extracted from purple sweet potato, impatiens petals and azalea petals. The effect of temperature, pH value and fish spoilage on the indication label was studied. It was found that the temperature had no effect on the label color. Purple sweet potato indication label was graying when the pH was 12.35, and impatiens indication label turned to greyish green. The colors of purple sweet potato label and impatiens label were changed obviously, and the color of azalea label was changed inconspicuously in the process of checking fish freshness. Taking impatiens indication label as an example for structural analysis, the color of functional groups on the main body of anthocyanin changed because of the products --- flavonoids and other substances resulting from nucleophilic or electrophilic rearrangement reaction under alkaline conditions. Anthocyanin can be used as freshness indicator of fish with good effects.