high selective and sensitive fluorescent sensor for the detection of cyanide was developed based on the conjugated of anthracene and hemicyanine. By the nucleophilic attacking of CN− to the indolenium C-2 atom of the sensor, the ICT progress (Intramolecular Charge Transfer) was blocked with color changed and fluorescence enhanced. The live cell fluorescent experiments demonstrated the value of the sensor in tracing the CN− in biological systems. Short responding time (less than 1 s) and excellent water-soluble ability (only 20% organic solvents needed in the detection) provided a broader application prospect in the practical application. The sensing mechanism was well rationalized with the aid of TD-DFT (time-dependent density functional theory) calculations.