Abstract: In order to get highly purified Omp protein of Candidatus Liberibacter asiaticus for function research, three fragments of the omp gene were amplified from infected citrus template with PCR. Then the three fragments were cloned into pET32a vector to construct pET32a -omp prokaryotic expression recombinant plasmid. The plasmid were then transformed into E. coli cell BL21(DE3). After that, Omp (His tag) fusion protein was induced with IPTG and detected with SDS-PAGE electrophoresis. In the end, Omp fusion protein was purified with nickel column. The result showed that two fragments of the Omp protein were efficiently expressed in E. coli, after induced with IPTG on 37益. Expected protein (about 55 ku) were gotten after purification with nickel column.