Narrow band gap semiconductor materials were composited to a photoanode to improve its light response characteristics and the photoelectric conversion properties of dye-sensitized solar cells(DSSCs). The citric acid gel method was used to prepare the CoAl2O4 nanopowders and the X-ray diffraction spectra were utilized to analyze the effect of roasting temperature on crystal structures and particle sizes. Then, the surface morphology of CoAl2O4 was observed by transmission electron microcopy, the absorbances of CoAl2O4 nanopowders and CoAl2O4/TiO2 porous composite films were tested by UV-visible absorption spectroscopy and the band gaps of CoAl2O4 nanopowders were calculated. By using CoAl2O4/TiO2 composite films as the photoanode, the DSSC was prepared. The optical performance of the DSSC was tested by a solar simulator and a SourceMeter and the influence of doping CoAl2O4 on the photoelectric properties of a DSSC was investigated. The results show that the optimum roasting temperature of CoAl2O4 powders is 700 ℃; and its band gap energy is 1.69 eV, which means that it is a narrow band gap semiconductor material. Moreover, the performance of DSSC is the best and the conversion efficiency improves by 62% when the amount of CoAl2O4 powder is 1%(weight percentage). The stability of the CoAl2O4/TiO2 composite thin film cells is better than that of the pure TiO2 thin film cell. These results demondtrate that compositing CoAl2O4 to TiO2 can improve the conversion efficiencies of DSSCs.