Abstract: Beijing fatty chicken were chosen as the research materials. The changes of proteins,amino acid,ash,fat,cholesterol and lysozyme in different incubation periods were analyzed under the same incubation conditions. The results showed that during the hatching of chicken embryo eggs,the protein level increased gradually from hatching,and the protein levels of 10~16 d were increased by 2.19% compared with fresh eggs. In the late incubation period,the proteins were gradually absorbed by the embryos and the content decreased slightly. The percentage of essential amino acids(EAA/TAA)was 47.85%~51.20%,which was close to the WHO/FAO ideal protein standard,which could provide the human body with more abundant essential amino acids. The tasty amino acid content in the total amino acid contents(FAA/TAA)was 37.97%~41.06%. Cholesterol and fat contents generally showed downward trends,the fat content decreased by nearly 1.5 times,and the ash content basically increased steadily from 1.07% to 1.65%. Lysozyme has anti-inflammatory and antibacterial activity. During hatching of chicken embryo eggs,lysozyme activity increased from 170 U/mg to 390 U/mg. The results of this study provide a reference for the development and utilization of nutritious eggs products and the study of natural antibacterial agents.