CD4 protein is present on the surface of 65% of human T cells, it plays an important functional role in the course of human immunodeficiency virus 1(HIV-1) infection. The difference in various CD4 proteins raise the great interest and necessary to investigate. In this project, the sequence diversity and structure difference among 15 species will be focused, and many free tools for biological data analysis, such as MEGAX and PyMOL. The result is that the more similar species evolve, the more similar or even the same length of CD4 will be, and the coverage of CD4 will also become the same.