A new very sensitive and selective fluorescent phenothiazine probe for the recognition of cyanide ions in an aqueous environment was prepared. The detection mechanism depends on the nucleophilic addition of cyanide ions to the fluorescent probe to result in fluorescent change go together with color change from purple to yellow. The prepared phenothiazine sensor was employed for invention of test strips able to recognize cyanide in aqueous media. It was found that the phenothiazine probe could selectively detect cyanide ions. When adding cyanide anions, the color of the yellow phenothiazine solution in dichloromethane changed to yellowish green, while a stronger green emission was monitored under UV lamp. Furthermore, the existence of 10 equivalents of other anions, including AcO−, HSO4−, Cl−, Br−, I−, H2PO4−, did not result in apparent variations in the UV-Vis absorption and fluorescent emission spectra. The recognition limit of phenothiazine probe to cyanide aions was 7.2 × 10−8 mol/L in dichloromethane.