Abstract: Phycobiliproteins are ligh-t harvesting proteins present in cyanobacteria. The most important step in phycobilin biosynthesisis the phycobilin addition to the apophycobiliproteins. In vivo, the correct attachment of most chromophores is catalyzed bybinding-site and chromophore-specific lyases, of which only few have hitherto been characterized. Phycoerythrocyanin have twosubunits. Bsubunit of phycoerythrocyanin is made of 171 amino acids and the binding-sites of phycobilin addition to the apophycobiliproteinsare Cys- 84 and Cys-155. The protein encoded by gene alr0617 was proved to be the lyase of Cys-84 of B- PEC. Bsubunit of phycoerythrocyanin ( PCB-PecB( C155I) ) was obtained by the in vivo reconstitution. The veracity was shown throughthe absorption spectra and the fluorescence spectra. After denaturation in the dark, with urea in the presence of hydrochloric acid( pH= 2), the phycobilin ( PCB) was not destroyed. The phycocyanobilin peptides were obtained from the natural subunit ofphycoerythrocyanin( B- PEC) and reconstituted PCB-PecB( C155I)hydrolyzed by pepsin, respectively. With Chromatography ana-lysis of high pressure liquid chromatography, we make a comparison of the retention time between the natural and the reconstitutedpept ides. The results showed that genes for the lyase ( alr 0617) catalyzed PCB attachment sites at Cys-84 in B-PEC.