In this paper, high-quality CdSe colloidal nanocrystals were synthesized by an improved Sol-Gel green technique. These colloidal nanocrystals were characterized by different techniques: Transmission Electron Microscopy (TEM) showed that the diameter of colloidal nanocrystals is about 3 nm; X-ray diffraction (XRD) demonstrated that CdSe colloidal nanocrystals formed in cubic phase; Fourier Transform Infrared spectroscopy (FT-IR) was employed to study the chemical compounds of as-prepared sol; UV-visible absorption spectroscopy was used to evaluate optical properties of prepared CdSe colloidal nanocrystals, which indicated that the absorption peak is around 500 nm; Photoluminescence (PL) spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 50.2% with 440 nm excitation wavelengths. Experimental observation has shown that highly stable CdSe colloidal nanocrystals with a strong green emission were synthesized. The mentioned optical properties have not been reported before.