In this paper, anatase TiO2 nanoparticles (14nm) were coated on the surface of piezoelectric PbTiO3 single crystal fibers by a secondary hydrothermal method, thus a p-n junction was formed at the interface between TiO2 and PbTiO3. The PbTiO3 fibers were exposed to an external force (by ultrasound) to generate a dynamic piezoelectric electric field in the crystal, which incessantly separates the carriers and improves the photocatalytic efficiency of TiO2. When the ultrasonic frequency is 40kHz, the TiO2/PbTiO3 fibers have the highest photocatalytic degradation efficiency (96%) for methylene orange (MO), which is up to 60% improvement compared to TiO2 nanoparticles.