Abstract: Phage display technology is a kind of method which display peptides or proteins of high diversity on the surface of phage coat proteins. This technology establish a linkage between genotype and phenotype, which makes functional screen of peptides or proteins convenient. Peptides or proteins screened from phage display library have high specificity and strong affinity, and play an important roles in basic research and clinical diagnosis and therapy. With the development of phage display, it has been used in the in vivo selection. It has characteristics of high throughput selection so that it can reveal molecular profiles and the differences of molecular profiles expressed on the vascular surface of different organs. Studies of in vivo selection can provide experimental evidences for the targeting diagnosis and therapy.