Pure-phase flower-like CuO porous microspheres with a sheet-like subunit-assembled micro/nano structure are prepared by a facile “alkali-oxidizing solution etching assisted crystallization based on microscale Cu particles” route, which manifest greatly enhanced Li storage properties: the initial discharge capacity of ∼1220 mAh g⁻¹ and reversible capacity of ∼800 mAh g⁻¹ at a current density of 50 mA g⁻¹. Even cycled at a current density of 400 mA g⁻¹, they still deliver stable capacity with a comparable value of 666 mAh g⁻¹ after 200 cycles.