Free Fatty Acid (FFA), also known as Non Esterified Fatty Acid (NEFA), is mainly produced by the breakdown of neutral fats in the body and is an intermediate product in fat metabolism. It serves as a donor for cell membrane lipid structure and prostaglandin synthesis, as well as one of the important energy sources in the human body. Research has shown that adiponectin, pantothenic acid, and acyl stimulating proteins can promote a decrease in NEFA levels in the blood, while tumor necrosis factor- α、 Catecholamine hormones, interleukin-6, and leptin can lead to an increase in NEFA levels. In addition, the increase of NEFA level in the blood is closely related to cardiovascular disease, liver disease, diabetes and other related diseases. Therefore, the determination of NEFA level in the blood has been used clinically as an auxiliary indicator to evaluate and diagnose the above diseases.