Objectives To analyze the effect of Ac25 on the proliferation of AcMNPV (Autographa californica multicapsid nucleopolyhedrovirus) progeny virus and its function in virogenic stroma. Results AcMNPV is a model of baculovirus and is the most widely studied baculovirus. Ac25, as a single-stranded DNA-binding protein, is involved in viral genomic DNA replication. Viral proliferation assay showed that AcMNPV progeny virus could not be produced when Ac25 was knocked out, which indicated it was crucial for BV production. Absolute quantitative PCR analysis indicated that Ac25 was able to promote replication of the AcMNPV genome in host Sf9 cells. It was also found that Ac25 could increase the transcription level of 38k and vp39 late expression genes, and inhibit host cell proliferation. Conclusion Ac25 is highly accumulated in the nucleus and promotes progeny virus production by stimulating viral genome replication and up-regulating the expression of late genes. Two potential applications of vAc-Ac25-EGFP were proposed: an improved bac-to-bac eukaryotic protein expression systems and biopesticides.