Abstract: Objective To study the immunological characteristics of the spike (S) protein of SARS coronavirus (SARS-CoV) and analyze the feasibility of using this protein as the component for SARS vaccine development. Methods The two truncated fragments of S gene were separately cloned into the prokaryotic expression vector pET-15b and expressed in E.coli. The resulting recombinant proteins, rS_a and rS_b, were purified by affinity chromatography. The full-length S gene was cloned into the eukaryotic expression plasmid pSecTagB to prepare recombinant plasmid pSecS as the DNA vaccine to immunize BALB/c mice for inducing the secretion of anti-SARS-CoV protein. The immunological effect of anti-SARS-CoV antibody was tested with purified rS_a and rS_b proteins by enzyme-linked immunosorbent assay (ELISA). Results Both the truncated recombinant proteins were expressed in soluble forms and reacted specifically with the sera from immunized pSecS mice and clinically diagnosed SARS patients. The prokaryotically expressed recombinant truncated S protein had similar antigenicity with SARS-CoV S protein. Conclusion The recombinant protein could be used as an antigen for detecting the serum of SARS CoV-infected patients. The SARS-CoV S gene vaccine could induce the production of specific antibody, which offers clues for the research of SARS DNA vaccine.