Nanowires of SrFe12O19 with diameters of similar to100 nm and lengths of -2.5 mum have been successfully synthesized in a hydrothermal cell at 180degreesC with an 0.35T magnetic field applied. The growth behavior of the nanoparticles was compared with that under zero magnetic field. The X-ray diffraction patterns indicate that both of the two processes result in formation of pure SrFe12O19, however transmission electron microscope observations show that the morphology of the particles changed from flake-like in zero magnetic field into nanowires in a magnetic field. Compared to the sample obtained under zero magnetic field, the as-prepared one exhibits a higher saturation magnetization. The possible underlying mechanism responsible for the morphology change and the magnetic properties improvement were discussed. (C) 2004 Elsevier B.V. All rights reserved.