Black blood spots on nails may be caused by nevus of onychomycosis, melanoma, trauma and other diseases, which need to be improved by general treatment, medication and surgery. 1. Nevus of Onychomycosis: Nevus of Onychomycosis may cause black blood spots on nails, which is mainly treated by surgery, and the common surgical method is surgical excision, which is convenient to improve the symptoms of local black blood spots. 2. Melanoma: black blood spots on nails are considered to be related to melanoma, and patients are suggested to choose surgical excision treatment. If surgical treatment is not suitable, oral drugs such as Vimofenib and Temozolomide can be taken to promote the recovery of the disease. 3. Trauma: trauma may lead to black blood spots on nails, patients need to protect nails to avoid secondary damage, you can use hydrogen peroxide, povidone iodine to disinfect the affected area. If necessary, you can go to the hospital for nail extraction surgery, and then use medicine on the wound to promote the healing of the injury. The causes of black blood spots on nails are not unique, and it is recommended that patients go to regular hospitals and cooperate with doctors for standardized treatment.