Gray nails, also known as onychomycosis, darkening is part of the disease progression. Nail fungus, is caused by dermatophyte infection of the nail lesions, fungi will invade the nail bed, resulting in thickening of the nails, grayish-yellow color, uneven nail plate, may cause the nail color is grayish-brown, as well as nail plate shedding and other symptoms, so nail fungus black is belong to the normal progression of the disease. Treatment of onychomycosis can be clinically through external drug therapy, as well as systemic drug therapy, external drugs because it is not easy to enter the nail plate, it is recommended to use a knife or a nail file to remove as much as possible of the diseased nails, and then use urea ointment to seal the package, and so on the diseased nails soften and peel off, and then use the antifungal drugs, for example, amorphophallus nail coating, cyclo-pyridonium ointment and so on; oral drugs have fluconazole, terbinafine, and so on. It is recommended that patients with onychomycosis go to the hospital in a timely manner, and drugs need to be used under the guidance of a professional doctor.