For the first time, it was found that low-valence additives could be employed to improve the conversion efficiency of dye sensitized solar cell. It was experimentally discovered that by forming nonstoichiometric compound, Ti3+ was located in the lattice of TiO2 film, generating surplus electrons within the film and affecting the morphology of TiO2 particle. The improvement of the conversion efficiency of the solar cell was mainly due to the increase of short circuit current along with the content of Ti3+. The surface of the TiO2 particle became more coarsely after TiCl3 added and the absorbed dye molecules was increased. It was another reason of the improvement of conversion efficiency.