Tongue diagnosis is an important diagnostical method of traditional Chinese medicine. The accuracy of tongue diagnosis can be improved by tongue characterization. Tongue area segmentation are important contents of preprocess of tongue image The use of computer vision technology to achieve the objective of tongue diagnosis of Chinese medicine is of great significance. The first task of objective analysis of tongue images is to extract tongue area out. The first step is to use median filter to remove noise image. The second step is transforms the image color space to HIS color space, Then the utilization dual Snakes algorithms obtain the accurate and complete tongue image. Through testing, the method has proved to be satisfactory for tongue image segmentation.