Recently, a new method to produce Au nanoparticles (Au-NPs) by in situ reduction of a Au salt using 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (Tiron) in water was reported. The Au-NPs of 8 nm in the typical average size were adsorbed by ionized Tiron and were dispersed in sol by electrical repulsive force. By addition of titanium butoxide, titanium hydroxide was coated onto Au-NPs via ionized Tiron and, the core-shell particles of Au@titanate were successfully created. Such nanocomposites had high photocatalytic effects for the decomposition of Methylene Blue.