The CdSe nanoparticles have been synthesized via wet chemical method using citrate as surfactant agent. The prepared nanoparticles are mono – dispersed in aqueous solution with strong green and orange emissions. The investigation of photoluminescence emission properties shows a photostability of the nanoparticles in different pH environment. The photostability also has been examined by observing the evolution of fluorescence spectra and quantum yield with storing time. The results show that the CdSe nanoparticles have high photostability which is almost unchanged after many months, and promise to be suitable for biolabeling.