CM, VLDL and LDL coagulate in a polyanionic environment to form a polymer and are masked by the polymer. High-density lipoprotein (HDL) form soluble compounds under the action of a surfactant, so that HDL-C can directly react with enzyme reagents containing cholesterol esterase (CE) and cholesterol oxidase (CO) to produce hydrogen peroxide. Hydrogen peroxide is catalyzed by peroxidase (POD) in the presence of 4-aminoantipyrine (4-AA) and phenol (T-OOS) to form a red quinone compound,the shade is proportional to the amount of HDL-C.