Abstract: The urokinase peptide inhibitors were screened in a phage display 6-mer peptide library by three rounds of selection basically according to the method described by Smith. To improve the screening effectiveness and specifi city, we designed a novel screening method in order to remove most of urokinase substrates from the peptide library. The potential inhibitors of urokinase were riched. After sequencing the clones, several related peptides were determined. Two 6-mer peptides were synthesized and their inhibitory constants to urokinase were determined to be 　88.6　μmol/L and 32.5　μmol/L, respectively.

Key words: peptide library, urokinase, inhibitor, screen