The aim of this study is to develop the recombinant adenovirus vaccine (rAdV) candidates containing neuraminidase (NA) gene of H5N1 influenza virus and test in BALB/c mice the effect of cell-mediated immunity. In this study, two kind of NA gene (WtNA gene, the wild type; Mod. NA gene, the codon-modified type) derived from H5N1 influenza virus (A/Anhui/1/2005) were cloned and inserted respectively into plasmid of adenovirus vector, then the rAdV vaccines candidates (rAdV-WtNA and rAdV-Mod. NA) were developed and purified, followed by immunization intramuscularly (10(9) TCID50 per dose, double injection at 0 and 4th week) in BALB/c mice, the effect of cell-mediated immunity were analysed at 5th week. Results indicated that: (i) NA protein expression was detected in two rAdV vaccines candidates by Western blotting; (ii) the rAdV-Mod. NA vaccine could elicit more robust NA specific cell-mediated immunity in mice than that of rAdV-WtNA vaccine (P = 0. 016) by IFN-gamma ELIspot assay. These findings suggested rAdV-Mod. NA vaccine was a potential vaccine candidate against H5N1 influenza and worthy of further investigation.