The testing of food pigment content is an indispensable part in food safety detection. Edible indigo blue and bright blue, two basic types of cyanine, are selected for research. A cyanine identification and quantitative analysis method based on absorption spectroscopy is proposed. By comparing the relationship between the molecular structure and characteristic peaks of these two types of cyanine and combining with electron transition theory, the difference of absorption spectra between them is analyzed. The quantitative analysis of bright blue pigment in multi-component system is carried out based on the difference of characteristic peaks, and the final model is established. Results show that the model has very high fitting degree, the linear regression coefficient reaches 0.99, and the average detection residual reaches 1.8 μg/ml.