Black vertical lines on nails are commonly found in onychomatous nevus, nail psoriasis, onychomycosis, subnail hemorrhage and other diseases, which need to be clearly diagnosed and then removed by choosing medication, surgery and physical therapy. 1. Onychomycosis:Onychomycosis belongs to benign hyperplasia of pigment cells in the nail matrix, and usually does not need treatment. If the shape and color change suddenly in a short period of time, the nails can be plucked out or the lesion can be excised through surgery. 2. Psoriasis:After psoriasis invades the nails, it can also lead to black vertical lines on the nails. When treating psoriasis, it should be treated for the original disease, usually after psoriasis is well treated, the nails will return to normal, and it can be treated with glucocorticoid, such as dexamethasone, hydrocortisone, etc.; oral methotrexate treatment, etc.; and if necessary, it can be treated with laser and ultraviolet irradiation, to improve the symptom. 3. Onychomycosis: This disease is mainly caused by fungal infection of the nails, and can be treated with topical antifungal drugs, such as cyclopyrrolate, amorolfine, etc.; when the effect of topical drug treatment is not good, oral antifungal treatment, such as itraconazole, fluconazole, etc.; if necessary, through the surgical extraction of the nail treatment. 4. Bleeding under the nail: trauma and extrusion may cause localized bleeding of the nail, which is manifested as black vertical stripes. Generally, there is no need for treatment, and it will gradually improve as the nail grows. It is recommended that patients should follow the doctor’s instructions for reasonable treatment after a clear diagnosis, and strictly follow the doctor’s instructions for medication, not blindly self-medication.