Abstract: Nails diagnosis as a kind of traditional Chinese medicine diagnosis method has its limitations in modern healthcare. Using a digital microscope and a scanning electron microscope(SEM), nine different kinds of human nails, such as normal nails, wide nails, sunken flat nails, narrow strip nails, are studied. From the different microstructure morphologies of nails, three conclusions are drawn. First, the nail cuticle tissues of normal nails have a smooth and dense lamellar structure, with a laminated growth, a small interlayer gap and no defects or holes. While those of abnormal nails, have a damaged lamellar structure, which has a large interlayer gap and a rough surface with local holes or granular structure. Second, the secondary electronic signal images obtained from the SEM can indirectly infer the level of metal trace elements with atomic number less than 20 in nails. Third, combining the microstructure of nails and the macroscopic nail diagnosis, we can make their respective advantages complementary to each other and make the best of them both. Through the comparison of macro and micro characteristics of different nails, the feature of different kinds of nails can be analysed comprehensively, and through the analysis of all kinds of nails, we can infer the health of human body's more accurately. It is of great significance to the development of TCM "Nail Diagnosis".