Autographa californica multiple nucleopolyhedrovirus(AcMNPV) ac30 (orf30) is a highly conserved gene in lepidopteran baculovirus whose function is unknown. ac30 is located between nt 24315 to nt 25706 in AcMNPV genome, and encodes a putative protein of 463 amino acids with a predicted molecular mass of 54.7 ku. To determine the role of ac30 in the baculovirus life cycle, an ac30 knockout virus containing the AcMNPV genome was generated by using AcMNPV bacmid bMON14272 via ET-recombination in Escherichia coli. To rescue the phenotype of the ac30 knockout, an ac30-repaired virus was constructed in which an ac30 gene copy with its native promoter and terminator element was inserted into the polyhedron (polh) locus of the ac30 knockout bacmid by transposition.Sf-9 cells were transfected withwt bacmid,ac30 knockout bacmid or the repair bacmid,respectively.All of the three virus bacmids could generate infectious virus. After infection of Sf-9 cells with wt virus, ac30 knockout virus or ac30 repair virus, all of the three viruses showed similar infection pattern.All these results indicated that ac30 gene was not essential for virus propagation in AcMNPV life cycle.