Nitrogen-doped graphene (NG) was successfully synthesized by a novel, facile, and scalable bottom-up method. The annealed NG (NG-A) possessed high specific surface area and a hierarchical porous texture, and exhibited remarkably improved electrocatalytic activity in the oxygen reduction reaction in both alkaline and acidic media. Ab initio molecular dynamic simulations indicated that rapid H transfer and the thermodynamic stability of six-membered N structures promoted the transformation of N-containing species from pyrrolic to pyridinic at 600 ℃. In O₂-staturated 0.1 M KOH solution, the half-wave potential (E_1/2) of NG-A was only 62 mV lower than that of a commercial Pt/C catalyst, and the limiting current density of NG-A was 0.5 mA·cm^–2 larger than that of Pt/C. Koutecky–Levich (K–L) plots and rotating ring-disk electrode measurement indicated a four-electron-transfer pathway in NG-A, which could be ascribed to its high content of pyridinic N.