Cage-shaped protein, with its special structure, may have potential applications in biomedicine and nanotechnology. We developed a program CSPro (Cage-Shaped Protein) for efficient identification of cage-shaped proteins based on quaternary structure. CSPro is capable of revealing the corresponding cage-shaped feature more clearly and quickly than traditional visualization tools. Using CSPro, we have searched the full set of PDB (protein data bank) and three types of proteins are retrieved with notably large central cavities inside. CSPro can be used to validate if the quaternary structure of a protein is cage shaped in molecular simulation.