Spider nevus is a special kind of capillary dilatation caused by the dilatation and branching of superficial plexus arteries in the skin, which appears on the skin like a spider. Smaller ones are like a large pin cap, while larger ones can be more than 1cm in diameter with a slightly elevated center. If the center is pressed, the blood flow will be blocked and the spider nevus will disappear due to ischemia. They usually appear in the area of the superior vena cava, and are usually found on exposed areas such as the face, forearms, hands, and armpits, and may also involve the lips and nose, as well as other areas. The damage is often single or multiple, especially in the presence of liver damage. The disease occurs in 15% of the normal population and is particularly common in children. Most scholars believe that the formation of spider nevus is related to estrogen metabolism, and it is normal for adolescent girls and pregnant women to develop spider nevus due to increased estrogen content in their bodies. If spider nevus suddenly appears in men or elderly women, they should be alerted because patients with cirrhosis, liver cancer and chronic hepatitis with liver failure will also develop spider nevus because the liver’s ability to inactivate estrogen is reduced. Although spider nevus is one of the manifestations of liver disease in the skin, the presence of spider nevus does not necessarily mean that liver disease is present. Spider nevus may also appear in other cases, such as capillary dilation caused by mosquito bites or trauma. In addition, spider nevus can also appear in healthy people, people with rheumatoid arthritis, rheumatoid arthritis, and people with vitamin B deficiency. Traditional treatment methods include freezing, ionization, microwave, and CO2 laser treatment, but all of them will leave different degrees of scars, pits and skin fibrosis changes after treatment. Nowadays, spider nevus can be treated with dual-wavelength dye laser, which uses the principle of selective photothermal, sufficient pulse energy, specific wavelength, and rapid coagulation after selective absorption by hemoglobin, thus closing capillaries and achieving the treatment purpose. This method is less painful for patients, does not recur after healing, does not leave scar, normal skin is not damaged, and keeps the skin beautiful, which is a more ideal method for treating spider nevus. Dual wavelength dye laser has made epoch-making progress in the treatment of vascular diseases, and it is usually cured in 1 to 2 times, but if the spider nevus is larger, which means the dilated blood vessels are thicker, it may take about 3 times, and eventually it can be completely eliminated. After the treatment, the area should be free of water and rubbed with antibiotic ointment for 5 days, 3 times a day. From the 6th day onwards, pay attention to rubbing moisturizing and sunscreen every day to prevent discoloration, and avoid eating spicy and stimulating food for half a month.