Transition　metal　oxide　catalysts　have　been　the　focus　of　recent　research　for　the　oxygen　reduction　reaction　(ORR).　However,　the　relationship　between　morphology　and　electrocatalysis　of　metal　oxide　catalysts　has　not　been　well　studied　or　understood　hitherto.　In　the　present　work,　cuprous　oxides　(Cu2O)　with　three　different　morphologies　(sphere,　octahedron,　and　truncated　octahedron)　have　been　synthesized　employing　a　potentiostatic　electrodeposition　method.　The　as-prepared　Cu2O　has　been　characterized　by　X-ray　diffraction　(XRD),　X-ray　photoelectron　spectroscopy　(XPS),　scanning　electron　microscopy　(SEM),　and　transmission　electron　microscopy　(TEM).　Three　different　shapes　of　Cu2O　crystals　were　used　to　study　the　shape-dependent　electrocatalytic　properties　for　ORR　in　alkaline　media.　It　was　found　that　the　surface-specific　activity　of　Cu2O　with　truncated　octahedron　shape　toward　ORR　was　higher　than　that　of　Cu2O　with　a　sphere　or　octahedron　morphology.　The　morphology-activity　relationship　of　Cu2O　as　a　cathode　catalyst　was　further　studied　through　periodic　spin　density　functional　theory　(DFT)　calculations.　Comprehensive　analysis　of　electrocatalysis　exiperiments　and　DFT　calculations　reveals　that　Cu2O　as　a　truncated　octahedron　preferentially　exposes　the　(100)　crystal　planes,　which　are　beneficial　to　stronger　O2　adsorption　and　easier　activation　of　adsorbed　O2　on　the　surface　of　Cu2O.　This　finding　furthers　our　understanding　of　Cu2O　catalysis　and　provides　new　light　on　the　relevant　catalyst　design　criteria.　©　The　Royal　Society　of　Chemistry　and　the　Centre　National　de　la　Recherche　Scientifique　2018.