The present invention provides an isolated antibody capable of binding to the receptor-binding domain of the spike protein of the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) so as to competitively inhibit the binding of the SARS-CoV to host cells. These mAbs or substances can be used: 1) as passive-immunizing agents for prevention of SARS-CoV infection; 2) as biological reagents for diagnosis of SARS-CoV infection; 3) as immunotherapeutics for early treatment of SARS-CoV infection; and 4) as probes for studying the immunogenicity, antigenicity, structure, and function of the SARS-CoV S protein.