The effect of various self-assembly time (8, 12, 24hrs) for Au nanoparticles (NPs) Thin film was investigated. When the self-assembly time is 8 hours, the efficiency of TiO 2 -Au photoelectrode is increased from 1.42% (for TiO 2 case) to 2.26% with an enhancement of 59%, and the fill factor is also increased from 51% to 57%. In the analysis of EIS, the charge transfer resistance of TiO 2 -Au photoelectrode and electron recombination rate of I 3 - at the TiO 2 -Au/electrolyte interface is lower than the TiO 2 photoelectrode. The results indicate that the adding of AuNPs can increase the conductivity and reduce the recombination of charge in photoelectrode.