Gold nanoparticles with mean size of 1 nm were placed on an indium tin oxide (ITO) electrode by arc plasma gun. The hole injection at ITO/organic semiconductor was significantly enhanced. Though the hole current was unstable upon the voltage scan, it can be substantially stabilized by the insertion of hyper-branched polystyrene thin layer between ITO and nanoparticles. The work function of ITO electrode was also increased. The ITO/HPS/gold nanoparticles structure was applied to the anode of an organic solar cell (OSC) with a bulk heterojunction active layer. The power conversion efficiency was significantly higher than that of OSC without anode buffer layer and almost comparable to that with a representative buffer material.