Abstract: This paper introduced a spectral imaging detection system which is based on a liquid crystal tunable filter. The system can get the samplesspectral image continuously. Its spectral resolution is up to 0.5nm. We processed and analyzed the image with Matlab software. The system was used to carry out in vivo test of Panacis quinquefolii and its pseudo products Platycodi. We obtained the fluorescence spectra image between 400nm～680nm. By comparing their characteristic spectral curve and calculating the correlation coefficient, we could differentiate the American ginseng and its counterfeit effectively. It provides a method for identifying the authenticity of Panacis quinquefolii.