Haemophilus parasuis is best known as the cause of Glasser’s disease, but the mechanisms underlying virulence differences on the molecular level are largely unknown. Nine strains (H1H9) of bacteria were isolated from unsound swine within farms in different regions of Guangdong province, then the 16SrRNA genes of the isolated strains were analyzed by PCR. The results of PCR combined with morphological observation and biochemical characterization showed that the isolated strains belonged to Haemophilus parasuis which had satellite phenomena and nonhemolytic characteristics. The nucleotide sequence similarities of hhdA genes between the isolated strains and Haemophilus parasuis srains SH0165 and HPS59 are 98%100% and nucleotide sequence similarities of hhdA genes among the isolated 9 strains are 99.0%99.9%. The phylogenetic tree showed that the isolated strain H1, H2, H8 and H9 belonged to one cluster. The deduced amino acid sequences of hhdA gene from the isolated strains were similar to the amino acid sequence of the hemolysin from other Haemophilus bacteria. RT–PCR indicated that the hhdA gene was expressed in all of the isolated strains. This study would be helpful for identification of virulence gene and for pathogenic mechanism study of Haemophilus parasuis.