According to published nucleotide sequences, ORF4 gene of barley yellow dwarf virus GAV (BYDV-GAV) was synthesized by reverse transcription-polymerase chain reaction (RT-PCR).The BYDV-GAV ORF4 gene was expressed in baculovirus -insect cell expression system efficiently, and western bolt analysis confirmed its expression product. Confocal laser scanning microscopy showed that GFP: ORF4 fusion protein was associated with the nuclear envelope of insect cells. By expressing the N- and C-terminal regions of ORF4-encoding product (P4) in insect cells combined with structure prediction, it was found that the N-terminal region of P4 containing four α-helices is required for targeting P4 to the nuclear envelope. These results provide a base for biological function of ORF4 gene during systemic infection of BYDV-GAV in host plants further.