Two strains of local nucleopolyhedrosis virus were isolated from dead Spodoptera litura larvae fed on tomato and maize in Ho Chi Minh city and Ba Ria - Vung Tau province. For the molecular identification of the virus, polyhedra (occlusion bodies [Obs]) were isolated from insect cavaders and purified, subsequently, total DNA extraction was performed and polyhedrin gene was amplified by PCR using specific poth gene NPV primer pair. After poth gene sequencing, Blast search in NCBI GenBank showed that the the nucleotide and deduced amino acid sequences of the poth genes obtained from S/NPV H1 and S/NPV H2 were highly similar with each other and with other S/NPVs available in Genbank and thus confirmed that both strains were Spodoptera liIura nucleopolyhedrosis virus. Quantitative determination of DNA in occlusion bodies using real-time PCR displayed the difference between the two strains, The number of DNA copies in S/NPV H2 occlusion bodies is much higher than that in S/NPV H1's ones, namely 500-1000 copies/OB vs 7-18 copies/OB. In the laboratory bioassay the LC50 values of S/NPV H1 and S/NPV H2 strains on 3rd larvae were 8.84 x 102 PIB/ml and 6.21 x 102 PIB/ml, respectively.