Perovskites with ABO(3) structure are the potential catalysts to replace the noble metals used in environmental catalysis, e.g. CO oxidation, volatile organic compounds (VOCs) and soot combustion. Herein, a novel double shelled porous perovskite-type LaNiO3 nanocage (assigned as LaNiO3-Cage, with dual cage or cage in cage structure) was successfully synthesized via a facile hydrothermal method for the first time. LaNiO3-Cage displayed superior activity and stability for CO oxidation. The morphology and structure properties of the samples were confirmed by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), High-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), Elemental mapping, Powder Xray Diffraction (PXRD) and N-2 adsorption/desorption techniques. The inherent morphology-activity relationship was investigated through Temperature-Programmed Reduction with Hydrogen (H-2-TPR), Temperature Programmed Desorption with Oxygen and Carbon monoxide (O-2-TPD and CO-TPD), and X-ray Photoelectron Spectroscopy (XPS) methods. LaNiO3-Cage showed superior catalytic performance among all the comparison samples (with lowest Ea, highest reaction activity, rate and TOF value) which should be ascribed to its special double-shelled porous nanocage structure (main factors) as well as larger surface areas and more active surface oxygen species. It should be noted that the outstanding catalytic performance of LaNiO3-Cage is well correlated with its special morphology structure. The porous double-shelled LaNiO3 nanocage prepared in this work can be used to design other type of catalysts with the similar morphology as novel nanoreactors.