Objective To study the characteristics of neutralization antibody in mice induced by DNA vaccines of hemagglutinin(HA) of novel H1N1 influenza A virus(2009H1N1).Methods HA encoding plasmids of 2009H1N1 or 1918H1N1(2009HA or 1918HA)were constructed.25 μg or 200 μg dosage of 2009HA plasmids were used to immunize the mice,the total antibody of anti-20O9HA or cross-reactive antibody were assayed by ELISA using 2009HA or 1918HA protein as capture antigen,and the neutralizing antibody were assayed by two kinds of virus pseudo - particles(pp) of 2009H1N1 and 1918H1N1 .Results During of 4 to 16 weeks after boost immunization,in two groups of mice immunized with 25 μg or 200 μg dosage 2009HA plasmids,both total antibody of anti-2009HA and neutralizing antibody to 2009H1Nlpp reached the similar level(P ＞0.05),and there were cross-reactive antibody to 1918HA protein in two groups of mice serum,with similar titers of cross-neutralizing activity to 1918H1N1 pp(P ＞0.05),Conclusion A low dosage DNA vaccine encoding HA of 2009 H1 N1 virus is able to induce persistent and high level of neutralizing antibody,and may be potential valuable vaccine against the new emerging influenza virus.