To overcome the dendrite formation of metallic lithium anodes, polycrystalline Li3N films are coated on Li foil by an ex-situ nitridation method. The electrochemical performances of the Li3N-modified Li electrodes are investigated by galvanostatic charge/discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) to determine the optimized nitridation condition. The morphologies and structures for the pure Li and the Li3N-modified Li electrodes, both before and after cycling, are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The Li3N films on Li surface can efficiently prevent the contact between Li and the electrolyte, and reduce the side reaction, thus suppressing the formation of dendritic lithium effectively.