Abstract: CdSe@ CdS quantum dot was prepared by"one pot"two step reaction using tween-80/n-hexanol/cyclohexane/water system as reaction medium. Dynamic light scattering,X-ray powder diffraction,transmission electron microscopy,UV-vis absorption,photoluminescence spectra analysis and photocatalysis tests indicate that the product has cubic CdSe @ CdS core-shell structure and uniform size （about 7 nm）,the spectra move red greatly about 100 nm,and the degradation rate of P25 sensitized by the product to Rhodamine B is more than doubled,revealing that the material has a strong visible light photocatalytic activity.