A new method, using electron beam, has been successfully developed to prepare nickel nano-particles at room temperature under ambient pressure, without any catalyst. The structure, morphology, size, size distribution, optical properties, magnetic properties and the melting point have been characterized by X-ray diffraction (XRD), laser scattering particle size distribution analysis (LSPSDA), transmission electron microscopy (TEM), ultraviolet-visible spectrophotometer (UV-vis), vibrating sample magnetometer (VSM) and differential scanning calorimeter (DSC), respectively. The LSPSDA and TEM results show that average size of the nickel nano-particles is about 39 nm, which is in agreement with the calculated value from XRD using Scherer formula.