We constructed Pasteurella multocida strain C51-17 aroA mutant and characterized its virulence.Suicide recombinant plasmid of pBC-aroA-Tn903 was constructed with kanamycin gene and transformed into Pasteurella multocida by electroporation. aroA mutant strain of P. multocida was screened by kanamycin resistance and chloromycetin sensitivity and identified by PCR. Virulence of aroA mutant strain was tested in mice by intraperitoneal injection.The aroA mutant strain of P. multocida C51-17 was successfully constructed. Growth rate of aroA mutant strain was slower within the first 6 hour and similar to the wild-type strain in vitro. The virulence test indicated that aroA mutant strain was significant attenuated and no death was found in mice even inoculated at a dosage of 1.0 x 10(6) CFU.The virulence of aroA mutant strain of P. multocida was highly attenuated in mice. The results of this study will contribute to a better understanding of pathogenesis of P. multocida.