Abstract: There is a close correlation between HI titre of Haemophilus paragallinarum(Hpg) HA and protection from infectious coryza. According to the published hemagglutinin antigen (HA) gene sequence of Dalian strain of Hpg, a pair of primers was designed and synthesized for amplifing Hpg’s major protecting antigen (HA gene). A DNA fragment about 1 038 bp was obtained through PCR method from Dalian strain of Hpg. The HA gene was cloned into the expression vector pET-32a and overexpressed in E. coli BL21 (DE3). Hemagglutination test indicated that the purified recombinant protein possess hemagglutinating activity. Western blot test showed that the protein was recognized by the chicken antibody against the Hpg of serotype B. This is first study in China to express HA gene and analysis the recombinant protein.