Studies have shown that host actin is essential for baculovirus replication and assemblage. In order to further elucidate the function of actin in the late and very late infection stages, a recombinant virus vAc-ph/70GA were constructed using Bac-to-Bac system, in which eGFP-actin fusion gene under control of hsp70 promoter and polyhedrin gene (ph) with its’own promoter were inserted. vAc-ph, which only contains ph, was also constructed as control. After vAc-ph/70GA infected Sf9 cells, actin was expressed persistently. However, there were no polyhedra, while the control virus vAc-ph did produce polyhedra. Further analysis such as SDS-PAGE and RT-PCR did not detect the transcription and expression of polyhedrin after vAc-ph/70GA infected Sf9 cells, indicating that the late expression of actin inhibit polyhedra formation. Expression of actin, however, did not change the viral infectivity. It can be concluded that the persistently expression of actin during late stage of baculovirus infection inhibit the polyhedrin expression, and then the formation of polyhedra. Here, some results were shown by electro microscopy, SDS-PAGE and RT-PCR with vAc-ph/70GA.