Abstract: Using RT-PCR and RACE, the full-length cDNA (2535 bp) coding a V-ATPase subunit A (VAA) gene ofvaa was cloned and sequenced from the larval midguts of the Asian corn borer Ostrinia furnacalis (Guenée). The relative open reading frame (ORF) sequence consisted of 1854 nucleotides, which translated into 617 amino acids, coding for the OfVAA with predicted molecular weight of 68.01 kD and isoelectric point (pI) of 4.90. The sequence was identified as VAA because it shared the common structural features with V-ATPase subunit A, including two putative conserved domains ATP-synt_ab_N and ATP-synt_ab_C, and a Walker A (GAFGCGKT) motif and a Walker B (SMMAD) motif. The protein was successfully expressed using Escherichia coli and purified. The ligand blot assay showed that the purified OfVAA peptide could bind with Cry1Ac toxin and enhance Cry1Ac insecticidal activity against the Asian corn borer larvae. The sequence reported in this paper has been deposited in the GenBank database at accession No.: HQ434762.