Abstract: It is of an important step to segment a tongue from itS background view of the face in computer analysis of tongue image. Starting with the theory of mathematical morphology, a method to get a tongue segmented is presented based on mathematical morphology and HIS model, of which mathematical morphology is combined with HIS model to feature the image morphology upon using the image color information comprehensively. The experimental resultS show that this method is effective in segmenting tongue images.