Photocatalysis is an effective technology to solve environmental pollution. Ferroelectric ceramics, as a new type of catalyst, have been received widespread attention mainly attributed to the ability to reduce the recombination rate of photo–induced carriers and to improve catalytic performance by building a built-in electric field. In order to avoid the decrease of remanent polarization in ceramic bulks during the traditional poling technology and simplify the poling process, corona poling technology has been used for the poling of powders. Several researches indicated that corona poling could significantly improve the catalytic performance, while the relationship among the particle size, phase structure, and piezo–photocatalytic performance was still not so clear. Therefore, BaTiO3 (BT) nanoparticles with different particle sizes were prepared via sol-gel method and then polarized these powders for 1 h under a voltage of 6.56 kV. The phase structures and the lattice distortion before and after poling were carefully explored. In addition, the effect of corona poling on the piezo–photocatalytic performance of BT powders was investigated, Rhodamine B (RhB) was utilized as the target pollutant.