BiFeO3 (BFO) nanoparticles were successfully synthesized by a hydrothermal method assisted by a mineralizer at as low a temperature as 200 degrees C. The products were characterized by X-ray powder diffraction, transmission electron microscope, and physical property measurement system. It was found that KNO3 as a mineralizer played an important role in the formation of BFO nanoparticles, and the as-synthesized BFO nanoparticles showed an enhanced ferromagnetism at room temperature.