［Objective］ To establish a fast,sensitive,and accurate method for detecting carmine.［Methods］ Using Folium Nelumbinis;as the carbon source,carbon dots (FN-CDs ) were prepared using a solvent thermal method,and the preparation conditions were optimized using a single factor test.Study the factors that affect the fluorescence intensity of FN -CDs,the effects of coexisting substances on the detection system,and optimize the measurement conditions;Using FN -CDs for the determination of carmine content in food and exploring its mechanism of action.［Results］］ Using 0.6 g of Folium Nelumbinis,0.25 g of citric acid and 45 mL of formamide were reacted at 240 ℃ for 4 hours,and the fluorescence value of FN -CDs was the strongest.Rouge had a good linear relationship within the concentration range of 0~70 μg/mL,with an R2 of 0.996 4 and a detection limit of 0.57 μg/mL.The spiked recovery rates of grapefruit juice beverage and canned arbutu were 88.09%~102.49% and 97.73%~112.47%,respectively.［Conclusion］ This detection method has the characteristics of high sensitivity,good selectivity and high accuracy,and can be applied to the rapid detection of carmine in food.