A fluorescence switching property of a copolymer of piperidinyl s-triazine (PT) and p-(trimethylsilyl) phenylene vinylene (TPV) was investigated by utilizing redox reaction of electroactive iodides. A polymer having high fluorescence quantum yield was synthesized by Wittig polycondensation reaction with 4, 6-bis (4-formylphenoxy)-2-piperidinyl-s-triazine and 2, 5-bis (triphenylphosphonionmethyl)-1, 4-bis (trimethylsilyl) benzene dibromide, to make a copolymer of PT and TPV (PTTPV). The fluorescence of the polymer was easily modulated by external potential in a two electrode cell consisting fluorescent layer and polymer electrolyte layer. When the fluorescent polymer layer was doped with iodide ions, the cell showed reversible switching property by applied potentials within +/- 3V.