Serum albumin, also called clear protein, is the most important component of human plasma protein. Serum albumin acts in two main ways: first, to maintain the normal nutritional state of the body. The second is to maintain the plasma and other colloid osmotic pressure, because serum albumin has a very important role in the normal nutritional status of the human body. In chronic malnutrition, serum albumin concentration will be significantly reduced. When the nutritional status is improved, the concentration of serum albumin will increase. In addition to the role of maintaining the normal nutritional status of the human body, serum albumin also has the role of maintaining the plasma colloid osmotic pressure, because the plasma albumin molecular weight is small, but high density, can adsorb water in the blood vessels, if the serum albumin concentration decreases, water will infiltrate from the blood vessels to the outside of the blood vessels, there will be tissue edema.