Glutamic functionalized water-soluble perylene diimide, N, N'-di (L-glutamic amine)-perylene-3,4,9,10tetracarboxylic diimide (GAPTCD) has three absorbance maxima at 469, 498, and 534 nm and two emission peaks at 550 and 587 nm. Owing to the highly negative electrostatic potential of the perylene plane, the perylene derivative showed good water solubility and strong fluorescence in alkali and neutral solutions. Both the absorbance and emission intensities decreased with the decreasing of pH from 9.66 to 5.92. This could be ascribed to the pi - pi stacking produced by H+ at the carboxyl group due to its electron accepting nature. Electrostatic potential maps also indicated that GAPTCD can exist stably in basic to weak acidic aqueous solution. Then GAPTCD was successfully applied as a high performance fluorochrome for imaging of living hela cells.