Nanoporous film electrode is a crucial composition of dye-sensitized solar cells, which influences the photoelectric conversion performance. To improve the property of the photoelectrode, different modification methods by using different concentrations of TiO2 sol are investigated. The crystallite size and phase of the nanoporous TiO2 particles and the TiO2 sol after sintering are studied with X-ray diffraction. The microstructure morphologies of the conductive glass and the films are determined by the high resolution transmission electron microscopy and the field emission scanning electron microscopy. The influences on electron lifetime n and the electron transit time d are analyzed by intensity-modulated photocurrent spectroscopy and photovoltage spectroscopy from the mechanisms of electron transport and back reaction kinetics. It is found that the back reactions are well suppressed under dark conditions after sol modifications. n is effectively extended and d is also shorten correspondingly by any kind of sol treatment. The short-current density and the photoelectric conversion efficiency are increased by 10.9% and 11.9% separately, when 0.10 molL-1 sol modification is applied both to the conductive glass and to the nanoporous TiO2 film at the same time.