Nanoparticles of CdSe nanoparticles have been synthesized in aqueous solution by reacting cadmium chloride (CdCl2.2.5H2O) and sodium hydrogen selenide (NaHSe) in presence of capping agent 3- mercaptopropionic acid (MPA). They are irradiated with a 2 MeV electron beam at a dose of 100, 200 and 300kGy. The effect of electron beam irradiation at different doses on the structural and optical properties of the prepared CdSe QDs is studied at different concentrations. Both the irradiated and unirradiated CdSe quantum dots have been characterized by XRD, TEM, EDX, UV-Vis spectroscopy, and photoluminescence spectro scopy. The XRD measurements of the functionalized CdSe quantum dots showed that these quantum dots have a cubic phase with zinc blend structure. The TEM measurements depicted that these quantum dots are monodispersed with spherical shape size about 5 nm. The EDX measurements indicated that the prepared quantum dots are highly pure and there are no impurities in the structures. The obtained CdSe NPs exhibit a relatively narrow PL band, as well as a high PL peak in the yellow spectral range. The irradiated CdSe@MPA QDs exhibit high photochemical stability and hold a good potential to be applied in optoelectronic devices.