Using a 2D Co-based MOF as precursor, a core-shell nanostructure consisting of Co3O4 nanoparticles and N-doped carbon matrix (Co3O4@N/C) was prepared by hydrothermal reaction between the carbonized MOF product and graphitic carbon nitride (g-C3N4) nanosheet. The Co3O4@N/C nanocomposite combines the advantages of N-doped carbon nanomaterials (high nitrogen content, good conductivity and high stability) and Co3O4 nanoparticles (high electrocatalytic activity), thus showing excellent catalytic performance for oxygen reduction reaction (ORR). The Co3O4@N/C presents an almost same onset potential and half wave potential with Pt/C, but more positive than those for the N-undoped counterpart. The electron transfer number of 3.73 for Co3O4@N/C is closer to 4, but bigger than that for the N-undoped product (3.53), indicating that the Co3O4@N/C catalyst gives rise to a nearly 4e mechanism. The Co3O4@N/C shows better methanol tolerance and long-term durability than the N-undoped product and Pt/C catalyst. The excellent ORR performance originates from the synergistic interaction between Co3O4 and N-doped carbon in core-shell structure. This study might give a good method for the synthesis of MOF-derived carbon nanocomposite for ORR electrocatalyst.