Autographa califonica nuclear polyhedrosis virus (AcNPV) DNA from larvae of lepidopteran infected by AcNPV has been isolated. The EcoRI fragments of AcNPV DNA have been cloned using plasmid pBR325 as a vector. The polyhedrin gene fragment containing recombinant plasmid pAc-18 was isolated through in situ hybridization. For the convenience of further construction the EcoRI insertion fragment was cloned into pUC-8. Thus plasmid pUAc-2 was obtained. The results of restriction mapping of pAc-18 and pUAc-2 and part of the sequence were reported. The polyhedrin promotor was known to be one of the most effective promotor useful in the expression of foreign genes in the insect cells.