The nail is located at the front of the hand and foot, and no human activity can be carried out without the hand and foot. In daily life, the nail is susceptible to irritation, attack and damage by various external physical and chemical factors, leading to nail disease. Nail disease is a collective term for lesions of the nail bed, perineum and nail plate. The occurrence of nail disease not only affects aesthetics, but also affects people psychologically and socially. Clinically, nail disease can be divided into nail fungal disease and non-fungal nail disease. Nail fungal disease (commonly known as gray nails) is the most common nail disease. Fungal infections are the culprit of nail fungal disease. Nail fungal disease is contagious, so it is important to detect, diagnose and treat it early. Clinical treatment usually requires longer-term antifungal drugs such as terbinafine and itraconazole. In addition to nail fungal disease, there is also a class of disease DD non-fungal nail disease with symptoms very similar to nail fungal disease clinically, people are easy to treat them as nail fungal disease, so the treatment is often failed. Non-fungal nail disease is complex and can be caused by multiple factors such as genetics, trauma, occupational factors, systemic diseases, micronutrient deficiencies, drug side effects, perinail inflammation, and subxiphoid nail tumors. Many non-fungal nail diseases are misdiagnosed as nail fungal disease, prompting patients to take a variety of topical or oral antifungal drugs for a long time, causing unnecessary economic burden to patients, and treatment failure is very likely to increase the psychological burden of patients, and even affect normal social activities due to the fear of nail fungal disease contagious. The most important reason why nail disease is misdiagnosed is that we attribute all nail diseases to fungal infections and do not know enough about non-fungal nail diseases. Clinically, the treatments for the two are very different. Therefore, it is extremely important to clearly diagnose nail fungal disease and non-fungal nail disease. Before treatment of nail disease, we must use practical tests to differentiate between the two. The most basic tests for nail disease include direct fungal microscopy and fungal culture, which are the most commonly used methods for diagnosing nail fungus disease. For non-fungal nail disease with an unknown diagnosis, we usually perform a variety of disease screening, including trace element testing and, if necessary, nail histopathology biopsy.