[en] Exploring metal-free electrocatalysts with high efficiency and lower cost for oxygen reduction reaction (ORR) is necessary to realize the commercialization of fuel cells. In this paper, the ORR mechanisms on nitrogen-doped graphdiyne (GDY) are investigated using the first principles calculations. It is found that the GDY doped with sp-hybridized N at acetylenic sites can activate molecular oxygen (O₂). The kinetically most favorable reaction pathway is O₂  →  OOH  →  O  +  H₂O  →  OH  →  H₂O, which is an efficient four-electron ORR process. The first reaction step O₂  →  OOH is the rate determining step (RDS), and the energy barrier is 0.61 eV. The energy barrier of RDS is smaller than that of pure Pt (0.80 eV). Therefore, these results illustrate that sp-hybridized N-doped GDY is a promising carbon-based metal-free ORR catalyst. (paper)