Based on a specific nucleophilic addition reaction with cyanide, a dicyano-vinyl-containing conjugated polymer (P1) has been designed and synthesized as a colorimetric and fluorescent chemosensor for cyanide anion. The combination of advantages of both reaction-based sensors and conjugated polymer sensors offers its highly sensitive and selective recognition of CN-. The addition of CN- to P1 solution induced a change in the solution color from yellow-green to colorless, while no color change could be observed in presence of other common anions, by which CN- can be identified from other anions directly with the naked eye. At the same time, a 31.6-fold fluorescence quenching was achieved upon adding CN- into P1 solution. The fluorescence quenching has shown a linear response to CN- in the concentration range of 0.5-30 mu M. Furthermore, its detection limit for CN- can be as low as 14 ppb, which is among the best results for the fluorescent conjugated polymer-based cyanide chemosensors. Compared with its small molecular counterpart, P1 exhibits higher sensitivity and selectivity, wider linear region, and faster response.