The purified Beijing duck serum lipoproteins were observed by electronmicroscope for its shape and size. The distributions of total cholesterol and LCAT activities and their gradient gel elctrophoresis, the amino acid composition and partial amino acid sequences of each fragment of apo A-I were studied and determined, respectively. Furthermore, their hydrophilicity and hydrophobicity of α-helices were also studied and compared with human and other species. When the above results were integrated together they provided further evidence for the hypothesis that the cholesterol of Beijing duck is carried and transported by HDL instead of LDL and apo A-I played an important role in the cholesterol metabolism.