Diethylaminocoumarin with imidazole as the bridge unit and phenyl rings appended was synthesized by conventional condensing method and routinely characterized by nuclear magnetic resonance and high resolution mass spectra technology. The absorption and emission behavior were studied in various polar environment. It exhibit highly emissive character in methanol with 89% emission quantum yield. In solid state, the fluorescence color shifts to yellow part with emission peak around 563 nm. Emission decay in solid state demonstrates the single index character of the excited dye molecules. Together with the conformation derived from single crystal structure, balanced driving force between regular and irregular packing trend leads to the highly emissive character.