Well-designed novel dual core-shell g-C3N4@Fe/Sr@g-C3N4 nanosphere (FSCN-NS) is originally reported in detail as high efficiency of oxygen reduction reaction (ORR) electrocatalyst in both acidic and alkaline media for fuel cell. The g-C3N4 as the catalyst carrier plays a critical role in facilitating the formation of the hierarchically porous architecture with large numbers of Fe3C, FeNx(x = 1–3), SrCN2 and SrC2 active ORR segments. Furthermore, g-C3N4 as catalyst protector has a stable supporting effect against chemical corrosion, ensuring stability and durability of the as synthesized FSCN-NS for ORR in fuel cell cathode. Additionally, the introduction of Sr can produce metal-nitrogen-carbon bonds to provide active ORR sites, contributes to the formation of the hierarchically porous nanostructure. Thus, FSCN-NS exhibits high ORR activity with the onset potentials of 1.06 V and 1.08 V in alkaline and acidic media, respectively. Notably, half-wave potential, limiting current density, methanol tolerance and durability are all better than that of commercial 20% Pt/C catalyst and most of previously reported materials derived from other metal-C/N nanostructure. Thus, FSCN-NS is as promising cheap candidate to solve the main problems of sluggish reaction kinetics of the ORR, high cost and low durability for fuel cells and metal-air batteries in energy conversion and storage devices.