We synthesized β-CD modified poly(phenylene ethynylene) (Polym-1) by the Sonogashira-coupling reaction. Polym-1 consists of CD-dimer unit; Polym-1 is taken as a polymer of CD-dimer, poly(CD-dimer). Polym-1 is structurally interesting wherein a poly(phenylene ethylene) is flanked by two cyclodextrin groups. Polym-1 is soluble in water because bulky hydrophilic CD groups of Polym-1 increased solubility toward water. With a trace amount of aliphatic 1-adamantanecarboxylic acid, fluorescence color of Poym-1 in aqueous solution was changed from weak green to strong blue emission due to the dissociation of intermolecular π-stacking between the polymer wires. On the other hand, fluorescence quenching of Polym-1 took place by adding viologen having adamantine moiety because holding viologen groups on the side chain of Polym-1 via host-guest formation results in efficient electron transfer from the poly(phenylene ethynylene) backbone to the viologen moieties.