Health preserving by two instruments is the principle of "one yin and one yang" put forward by Chinese medicine, which holds that yin and yang are the fundamental laws of the universe. Using the function of yin and yang and five elements, we can choose different foods according to different diseases. Dietetic food is eaten according to meridian tropism and efficacy, which is effective. The principle of two instruments for health preservation is to promote the smoothness of symptoms and meridians through specific functions, and food nourishes specific meridians through specific composition combinations.