The patient’s finger purple, black has the following several diseases: 1, the most common factor is heart disease, in the heart blood supply is incomplete, there will be a weakening of peripheral circulation, the heart can’t give the peripheral circulation of blood supply, oxygen supply and energy supply, which will lead to the finger parts of the peripheral circulation weakening, the finger will appear purple and black. 2, the lungs function is reduced, for example, pulmonary arterial hypertension, chronic obstructive pulmonary emphysema, the patient will appear circumference and lack of oxygen and insufficient oxygen supply. The lack of oxygen and insufficient oxygen supply, under the premise of insufficient oxygen supply, the nail bed of the finger will also appear purple and black. 3, poisoning diseases, such as acute nitrite poisoning can also lead to cyanosis, especially the extremities of the end of the black, purple.