The Spodoptera litura nucleopolyhedrovirus (SpltNPV) gp37 fusion gene was inserted into the transfer vector (pBacPAK9), named pBacPAKSL37fus. The vector was cotransfected BT1-Tn5B1-4 (Hi5) cells with liner Autographa californica nucleopolyhedrovirus(AcNPV) DNA (BacPAK6).The purified, non-occluded body recombinant baculovirus (Ac-PAKSL37fus) was selected by successive 3 cycles of plaque purification. The inserted gp37 fusion gene under the control of polyhedrin gene could high-express gp37fus protein. At 24 hours post infection (hr.p.i), sf-21 cells infected with recombinant virus had a distinctive cytopathic effect compared to cells with wild type (w.t) AcNPV. Through successive 5 generation infections, cytotoxicity of the recombinant virus did not weaken. The result from infected beet armyworm larvae showed that mortality of test group infected with recombinant virus was 26 percent higher than the control group with parent virus at 60 hr p.i. The recombinant baculoviruses were co-embedded in insect with wt parent virus via subcutaneous injection. If again, beet armyworm larvae infected with the NPV isolated from dead insects, mortality of insects was 17% higher than that of the control.