Objective　This study was to provide the target antigen for the development of a Lyme disease vaccine and serodiagnosis reagent.Methods　We used the automatic DNA sequencing machine (Model 377) to detect the nucleotide sequence of the inserted part of the recombinant plasmid pBX1 from Borrelia burgdorferi B31 strain. The restriction enzyme map of the inserted part of pBX1 was analysed by using computer software. The expressed product of pBX1 in E.coli XLI-Blue MRF′ was analysed by using SDS-PAGE and western-blotting. Results　①DNA sequencing showed that pBX1 contained a 477bp inserted gene fragment,and when it was compared with the published sequence of the specific region of the gene of the 83kd antigen protein from Borrelia burgdorferi B31 strain,only one amino acid codon was different.②The restriction enzyme map of the inserted part of pBX1 was successfully constructed.③The recombinant plasmid pBX1 expressed a 29kd fusion protein in E.coli XL1-Blue MRF′after induced with IPTG.The recombinant fusion protein could be recongnized by rabbit polyclonal antiserum against Borrelia burgdorferi B31 strain. Conclusion　A recombinant plasmid which contains the gene fragment encoding the specific region of the 83kd antigen protein from Borrelia burgdorferi B31 strain has been successfully constructed.The recombinant plasmid can stably express 29kd fusion protein in E.coli XL1-Blue MRF′.These results could serve as a base of further studies on the usefulness of the fusion protein in serodiagnosis and vaccine for Lyme disease.