It was demonstrated that crystalline nickel fibers could be synthesized by a chemical method under the influence of magnetic field. The fibers would grow from a few nucleation points in the direction of magnetic field. We believed that ultra-fine nickel powders were first produced by chemical reduction. Kinetic measurements indicated that there was an induction period prior to the precipitation process. These ultra-fine powders were then magnetized and grew into fibers along the direction of magnetic field. The diameters of these fibers were strongly affected by the starting pH of the precursor solution, varying from 50 pm to around 1 mum when pH was changed from 11.5 to 14.5. On the other hand, when the magnetic field was above 50 Oe (Oersted), we could always obtain fiber with lengths over 5 cm. Both electrical and magnetic properties were also reported for these Ni fibers.