Two kinds of L-glutathione capped highly fluorescent CdSe/CdS core-shell quantum dots (QDs) emitting green and orange fluorescence at 350 nm excitation were firstly prepared by an aqueous approach and used as fluorescent labels, to link mouse anti-human CD3 which was expressed on human T-lymphocyte. UV-Vis absorption and fluorescence emission spectra of the as-prepared CdSe/CdS core-shell QDs were studied. Compared with the CdSe QDs, a remarkable enhancement in the emission intensity and a red shift of emission wavelength of CdSe/CdS core-shell QDs was observed for the two kinds of QDs emitting green and orange fluorescence. The TEM results showed that the as prepared CdSe and CdSe/CdS QDs dispersed well in aqueous solution, and their shape was approximately spherical, and the CdSe/CdS QDs nano particles emitting green fluorescence are of about 5 run in diameter. The two kinds of CdSe/CdS QDs were linked with mouse anti-human CD3 to image human T-lymphocyte. The fluorescent microscopical images of human T-lymphocyte labeled with CdSe/CdS QDs-CD3 and FITC-CD3 demonstrated that the fluorescent CdSe/CdS QDs exhibited much better photo stability and brighter fluorescence than FITC, showing a good application potential in the immuno-labeling of cells.