Abstract: Objective To construct pr okaryot ic expression plasmid of vacA gene of coccoid Helicobacter pylori.Methods VacA gene was digested with restr ictio n endonucleases from recombinant plasmid pMD-18T-vacA and was inserted into expression vector pET32a(+)by subclone technique,then the recombinants were transformed into E.coli BL21 and ident ified by restriction endonucleases digestion and PCR.Then the geneticaly engineered bacteria of including pET32a(+)vacA plasmids were induced by IPTG,the expression product was analyzed by SDS-PAGE and densitometric scanning.Results The positive recombinant plasmids pET32a(+)vacA were identified by restriction endonucleases dig estion and PCR,in accordance with the expected results.Sequence analysis showed that the vacA gene homology of coccoid.H.pylori and reported in GenBand was 99.2%.Plasmid pET23a(+)vacA could express a specific 156KD a protein in E.coli BL21,the protein accouterd for 15.5% of total protein of recombinant bacterial.Conclusion The prokar yotic expression plasmids,which contain vacA gene of coccoid H.pylori are successfully constructed.Plasmid pET32a(+)vacA can express specific protein in E.coli BL21.This work will help study ing the biologic character of VacA protein and DNA vaccine against H.pylori infection.