To develop sensitive and selective CN- chemosensors, a new imidazole-functionalized polyfluorene (P1) was designed and obtained conveniently, the fluorescence of which Could be completely quenched by Cu2+ ions at the concentration as low as 0.20 ppm in diluted solutions. By Utifizing the much higher stability constant of the complex of CN-and Cu2+, the quenched fluorescence of the solution of P1 by Cu2+ ions Could recover upon the addition of trace CN- anions, with the detection limit clown to 0.31 ppm, making P1 a novel, sensitive and selective cyanide probe.