In summary, we have characterized the SARS-CoV-2 RBD protein which exhibits strong binding to its cell-associated and soluble ACE2 receptors with human and bat origin. This RBD protein also demonstrated significantly higher binding affinity to ACE2 than SARS-CoV RBD. SARS-CoV-2 RBD protein could block S protein-mediated SARS-CoV-2 pseudovirus and SARS-CoV pseudovirus entry into their respective ACE2 receptor-expressing target cells, suggesting the potential of SARS-CoV-2 RBD protein as a viral attachment or entry inhibitor against SARS-CoV-2 and SARS-CoV. SARS-CoV RBD-induced antibodies could cross-react with SARS-CoV-2 RBD and cross-neutralize SARS-CoV-2 pseudovirus infection, indicating that SARS-CoV RBD-specific antibodies may be used for treatment of SARS-CoV-2 infection and that either SARS-CoV RBD protein or SARS-CoV-2 RBD protein may be used as a candidate vaccine to induce cross-reactive or cross-neutralizing antibodies for prevention of SARS-CoV-2 or SARS-CoV infection. Taken together, this study provides an essential foundation for the design and development of SARS-CoV-2 RBD-based vaccines and therapeutics.