Nanoscale magnetic materials have been receiving increasing interest for their potential applications. One-dimensional magnetic particles chain of polycrystalline nickel was prepared by a simple template-free method under magnetic field. Based on solution reduction reaction of Ni2+, metallic nickel was deposited and synchronously self-assembled into chains under magnetic field. The results show that the chain of polycrystalline nickel was several micrometer in length and several hundreds nanometer in diameter. VSM measurements indicate the magnetic properties of chains formed can be modulated by the reaction time and the solution concentration. It is suggested that the magnetic field be an effective and tunable way to the fabrication one-dimensional chains of magnetic materials.