Abstract: Motivated by the recent advances of transition-metal-nitrogen-carbon (TM-N-C) materials in catalysis, we investigate the electronic structure and transport properties of FeN_3-embedded armchair and zigzag graphene nanoribbons (FeN_3@AGNRs, FeN_3@ZGNRs) with different widths. The first-principles results indicate that the FeN_3 induces significant changes on the band structures of both ZGNRs and AGNRs, making the resultant systems quite different from the pristine ones and own room-temperature stable ferromagnetic (FM) ground states. While only FeN_3@AGNRs possess a significant spin-dependent negative differential resistance (NDR) and a striking current polarization (nearly 100\%) behaviors, due to that FeN_3 introduces two isolated spin-down states, which contribute current with different performances when they couple with different frontier orbits. It is suggested that by embedding FeN_3 complexes, AGNRs can be used to build spin devices in spintronics.