The CaMnO3 perovskites have been proposed as promising electrocatalysts for the oxygen reduction reaction (ORR) as substitutes for the noble metal. However, their ORR catalytic activities still need to be further improved. Herein, fibrous CaMnO3 catalysts with hierarchical mesoporous/macroporous structures for the ORR were prepared through a simple ion exchange process with biomass derivative calcium alginate as a precursor. Optimization of the synthesis conditions, in particular, the La doping content, is conducted. The as prepared CaMnO3 shows superior ORR performance in alkaline media with a limited diffusion density of 6.13 mA cm(-2). Furthermore, the ORR performance was further promoted by La-doping. The optimal La-doped CaMnO3 sample exhibits the most positive onset potential of -0.01 V, the most positive half-wave potential of -0.28 V (VS. Ag/AgCl), and a greatly enhanced limited diffusion density of 6.76 mA cm(-2). The improvement of catalytic activity for ORR can be attributed to the porous structure, the rich surface chemisorbed oxygen and the redox couple Mn3+/Mn4+. The as-prepared perovskite fibers have potential as low cost and efficient ORR catalysts. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.