In order to seek heterogeneous electrocatalyst with efficient catalytic activity for oxygen reduction reaction (ORR), Fe3O4-CNx composite reported in our previous work was studied as electrocatalyst for ORR and showed poor catalytic activity. To improve the catalytic activity, Fe3O4-CNx composite is modified by the CNx layers derived from lysine through pyrolysis. The physical characterization show that the coral-shaped morphology of the resultant composite (Fe3O4-CNx-Lys) is still retained, while the degree of its graphitic crystalline increases. Besides, Fe3O4-CNx-Lys has 364.7 m(2) g(-1) of surface area with hierarchical porous structure. Electrochemical tests show that the catalytic activity Fe3O4-CNx-Lys for ORR is not only higher than those Fe3O4-CNx, XC-72-Lys derived from lysine and XC-72 Vulcan carbon but also comparable to that of commercial Pt/C (20 wt%). Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.