During the experiment, diversified proteins were separated from hen egg yolk by ammonium sulphate rapid fractionation, and pure LDL was obtained after filtrating through Sephadex G-200 chromatography. After the qualitative detection of SDS-PAGE, the authors discovered that LDL consists of five major apoprotein. The Raman and infrared spectrum showed CH2 asymmetric stretching and symmetric stretching mode. However, the authors found CO stretching vibrations of protein peptide bonds and N+(CH3)3 asymmetric stretching vibration from the choline group in phospholipids. Laser Raman and infrared spectrum analysis of LDL provided useful information for studying their structure.