The purpose of decoction traditional Chinese medicine is to make full exhalation of medicinal materials active ingredients, thus it has the maximum effect of traditional Chinese medicine to treat disease. In order to detect the dissolution change of medicinal materials active ingredients in decoction process, this paper applys spectral imaging technology, with Chinese traditional medicine cortex phellodendri as an example, discussing its fluorescence intensity at different time in decoction process. And the analysis results reflect edgewise the dissolution rule of cortex phellodendri active ingredients.