We can prepare well-dispersed colloidal solutions of nanophosphors by liquid phase synthesis methods.One of characteristic optical properties of nanophosphors is transparency.Since the light scattering intensity is proportional to the sixth power of a particle diameter,nanosizing remarkably decreases the light scattering intensity.Nanophosphors with their diameters less than 50 nm can be dispersed in a matrix transparently to the eye because of the low scattering intensity of visible light.In this lecture,we mainly introduce our research on preparation and optical properties of YAG:Ce3+ and YVO4:Bi3+,Eu3+ nanophosphors and their transparent films.