There are many kinds of blood anticoagulants in blood collection reagents, and one anticoagulant is widely used, that is EDTA potassium salt. EDTA potassium salt has a variety of models, in which potassium is used more, but how about its principle and application? There should be some people who don't know it very well. Here we can look at its application fields and principles. EDTA dipotassium salt, also known as EDTA-K2 dihydrate, is a white crystalline powder, easily soluble in water and hygroscopic, with a molecular weight of 404.6. Deta dipotassium salt can protect blood cell composition, does not affect white blood cells, has the least impact on red blood cells, and can inhibit platelet aggregation, which is suitable for general blood test. However, apart from platelet separation test, it is not suitable for coagulation test and platelet kinetic energy test, nor for determination of calcium, potassium, sodium, iron, alkaline phosphatase, creatine kinase, leucine aminopeptidase and PCR test. EDTA dipotassium salt as anticoagulant principle, first we understand the principle of blood coagulation, and this can be divided into three parts, 1, the formation of prothrombin activator, 2, prothrombin activator in the presence of calcium ion to make prothrombin into active thrombin, 3, soluble fibrinogen in the role of thrombin into insoluble fibrin. Fibrin is like filaments, crisscross, and contains a large number of blood cells to form a jelly like blood clot. This is what happens to blood clotting. EDTA ions in the blood can be converted into calcium antithrombin, so that the blood has a great affinity for calcium.