In order to enhance the immune effect of H7N9 influenza virus HA DNA vaccine, the expression plasmids containing five repetitive dominant T epitopes or B epitopes, including B1 linear epitope or B2 conformational epitope, of influenza virus NP were constructed (NPT and NPB for short). BALB/c mice were immunized with H7N9 influenza virus HA DNA in combination with NPT or NPB, respectively. Twentyone days later, the mice were challenged with a lethal dose (20 LD50) of H7N9 influenza virus. The protective effects of NP epitope plasmid in combination with HA DNA vaccine were evaluated by detecting vaccine specific antibody titer in serum, survival rate, lung viral titer and body weight loss of mice. The results showed that all mice vaccinated with only HA DNA died after the mice were challenged with the lethal H7N9 influenza virus; the mice survival rate of HA+NPT group reached 100%; the survival rate of mice vaccinated with HA+NPB1 or HA+NPB2 groups was 30% and 75%, respectively. The levels of antibodies were increased in the mixed immunization group compared with the HA alone group. The antibody level of the mice was significantly elevated after HA+NPT mixed immunization. Their loss rates of body weight were significantly reduced, and the body weight recovered after 21 days of challenge. This study showed that the expression plasmid containing five NPpreferred T epitopes or B epitopes could enhance the immune effect of H7N9 influenza virus HA DNA vaccine, and mixed immunization of NP epitope plasmid and HA DNA vaccine could provide better protection against H7N9 influenza virus in mice experiments. The combination of HA DNA and epitope vaccine can save the vaccine dosage and reduce the cost of immunization, and provide a certain experimental basis for the clinical development of influenza  DNA vaccine.