This paper describes a new fluorescent chemosensor for phosphorylated peptide, which comprises a rigid trans-4, 4′-diazastilbene and two Zn (II)-Dpa (2, 2′-dipicolylamine) units; this chemosensor sequence-selectively binds to a (i, i+ 1) bis-phosphorylated peptide and displays a dual-emission fluorescence change.