Polycrystalline BiFeO3 nanoparticles (size 30-50 nm) were prepared by a simple microwave synthesis technique. The nanoparticles were characterized by XRD, TEM and TG-DTA. The applied experiments show that they are very efficient for photo-catalytic decomposition of organic contaminants under irradiation ultraviolet frequency. The as-obtained BiFeO3 nanoparticles also demonstrate strong ferromagnetism of about 0.045 microB/Fe at room temperature, which is in good agreement with theoretical calculations.