The following are the common clinical reasons for the blackening of the severed finger: First, superficial skin blackening, mostly seen in local skin bruising, manifested as the blackening of the finger, when the subcutaneous bruising is gradually absorbed, the symptoms of finger blackening can be completely relieved, and the function of the severed limb is not affected. If the whole limb is blackened, it is likely that the occlusion of the replanted blood vessels has occurred, and necrosis of the severed limb has occurred, so the severed finger needs to be removed and the proximal limb repaired. Third, if there is a temporary ischemia and hypoxia due to spasmodic constriction of the blood vessels of the severed finger, the limb will be blackened. In this case, the patient should completely quit smoking, local infrared irradiation of the distal limb to keep the limb fully warm, and release the vasospasm can promote the return of normal blood flow to the severed limb, thus reducing the symptoms of blackening.