To immobilize titania (TiO2) in a matrix and improve the photocatalytic efficiency, TiO2 nanoparticles decorated carbon nanofibers (TiO2-D-CNF) were prepared by ultra- sonication induced adsorption of TiO2 nanoparticles onto the surface of electrospun polyacrylonitrile (PAN) nanofibers, followed by first heat treatment in air and then calcination in nitrogen. The interfacial collision under ultrasonication was responsible for uniform decoration of TiO2 nanoparticles on polymer nanofibers. However, TiO2 nanoparticles were mainly located inside the carbon nanofibers (TiO2-I-CNF) and only some aggregates were observed on the nanofiber surface if the nanofiber composite was obtained by electrospinning the mixed polymer solution containing the nanoparticles. It was found that TiO2-D-CNF possessed both higher dye adsoption capacity and photo- catalytic efficiecy than TiO2-I-CNF due to its hierachical microstructure. The exposure of TiO2 nanoparticles on the CNF surface was beneficial for the adsorption of pollutant and thus photocatalytic performance.