Objective To understand the functions of ORF27 protein of the Thai isolated Helicoverpa armigera nucleopolyhedrovirus(HaNPV-Th) and explain the possible molecular mechanism of HaNPV-Th in passage effect.Methods ORF27 gene was cloned and amplified by polymerase chain reaction(PCR) from HaNPV-Th genome.The physical-chemical properties,subcellular localization,signal peptide,transmembrane structure and functional motifs were analyzed by the software of ProtParam,TMpred,SignalP and ScanProsite.The truncated ORF27 gene which lacked parts of the amino-terminal was expressed by bacterial expression system.Results The full length sequence of ORF27 was 768bp long and encoded 255aa with a molecular weight of 29.5ku.Several functional motifs on ORF27 were predicted by bioinformatics software.The truncated ORF27 recombinant expressed 35ku target protein mainly in the form of inclusion body.Conclusion ORF27 protein of HaNPV-Th is presumed to possess extensive biological activities.It may regulate various cellular signaling pathways,apoptosis and cell cycle,which are involved in passage effect.