Spider nevus is a manifestation of localized capillary dilatation, usually without self-conscious symptoms. Spider nevus is caused by the weakening of the inactivation of estrogen by the organism, and it is mostly located in the areas distributed by the superior vena cava, such as the face, neck, anterior chest, upper arms and so on. Spider nevus is characterized by its spider-like shape, surrounded by a network of small blood vessels similar to spider’s feet. When the center of spider nevus is pressed with a cotton swab, it can be seen pulsating, while the surrounding pseudo-feet disappears, and after the swab is picked up, the blood first fills up the center, then flows into the branches, and quickly recovers its original shape. The appearance of spider nevus is mostly suggestive of liver cirrhosis, and usually has no conscious symptoms. If spider nevus appears, one should consult a doctor in time and find out the primary disease under the guidance of a professional physician to avoid delaying the condition.