Real-time and visual monitoring fish freshness is crucial to safeguard food quality and consumer safety. In this study， a fluorescent probe CDI with a donor (D)-π-acceptor (A) structure was synthesized from 4-(dimethylamino) cinnamaldehyde and isophorone malononitrile to monitor the freshness of salmon in real time. The probe responded apparently to 13 amines and its fluorescence detection limit was as low as 9.91 μmol/L for the cadaverine produced during the spoilage process of aquatic products. The indicator label loaded with probe CDI+H+ was obtained by physically depositing probe CDI on fiber filter paper， and then hydrochloric acid was added to protonate it. When the indicator label was placed over salmon meat， the indicator label changed from white to light yellow until yellow， and the fluorescence gradually turned on from purplish pink to orange-red as the freshness of salmon meat decreased. By comparing with the total volatile base nitrogen value， it was verified that the indicator label loaded with probe CDI+H+ could effectively distinguish the three freshness levels of salmon by colorimetric and fluorescent dual response.