5-[4-(dimethylamino)benzylidene) pyrimidine-2,4,6(1H,3H,5H)]-trione (DMP-3H), the receptor was synthesized which played a chemosensor role for cyanide ion ($CN^{-}$) in aqueous solution with colorimetricand fluorescence turn-off responses. Upon addition of $CN^{-}$ ion into the solution containing the receptor, acolor change visible to the naked eye was observed from yellow to colourless and also, the fluorescence of the solution was immediately quenched. Moreover, DMP-3H exhibited a selective response to cyanide ion over many other anions such as $F^{-}$, $Cl^{-}$,$ Br^{-}$,$ I^{-}$, $SO^{2-}_{3}$, $OCN^{-}$, $ClO^{-}_{3}$ , $CO^{2-}_3$ , $IO^{-}_{3}$ ,$N^{-}_{3}$, $C_2O^{2-}_{4}$ and $SCN^{???}$. The detection limit toward $CN^{-}$ was $8.1\times 10^{-7}$ mol.L-1, which is satisfactory enough for monitoring $CN^{-}$ levels in physiological and environmental systems.