Nitrogen-doped carbon materials containing non-precious metal (TM-N-C) and Co-based oxides have been extensively investigated as promising catalysts for oxygen reduction reaction (ORR). Herein, we report a novel Co3O4/Co-N-C modified ketjenblack carbon (KB) catalyst via a one-pot and scalable pyrolysis process using cheap melamine, cobalt acetate tetrahydrate and KB as raw materials. Owing to the high specific surface area and good electrical conductivity, this KB-based catalyst exhibits remarkable catalytic activity with a half-wave potential of 0.798 V (vs RHE) and a limiting current density of 5.10 mA cm−2 in alkaline solution, which are comparable with those of the commercial 20 wt% Pt/C. More importantly, it displays superior stability to Pt/C, which makes it one of the most promising non-noble-metal catalysts. Al-air batteries with this catalyst are also tested and generate a maximum power density of 161.1 mW cm−2, which is close to that with 20 wt% Pt/C catalyst (161.9 mW cm−2). After the discharge for 18 h at 50 mA cm−2, the voltage degradation of Al-air battery with Co3O4/Co-N-C modified KB is 7%, while that using Pt/C is increased to 12%. By virtues of its remarkable performance, low cost and simple fabrication method, Co3O4/Co-N-C modified KB here can be used as an efficient ORR cathode catalyst instead of the commercial Pt/C for practical Al-air batteries.