Fall armyworm,Spodoptera frugiperda,is one of the most important pests on maize,which invaded into China newly. In order to determine the control effect of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) on larvae of S. frugiperda,the insecticidal activity and biocontrol effect of AcMNPV on S. frugiperda were studied and analyzed by the methods of bioassay and field efficacy test. The results showed that the median lethal concentration ( LC50 ) of AcMNPV acting on the 2nd instar larvae of S. frugiperda was 2.9×107 PIB/mL. The average control efficacy of 107 PIB/mL AcMNPV + Bt Suspension（1 500 mL/hm2）on S. frugiperda was 68.99% on the 10th day and 66.87% on the 15 th day after administration. Finally,DNAMAN 6.0 software was used to identify the DNA homology of the dead insects,and the results showed that the polh,lef8 and lef9 gene sequences sequences of the dead insect and the S. frugiperda were 100% identical. All the above results could further verify that AcMNPV may play a key role on controlling S. frugiperda. It is suggested that 107 PIB/mL AcMNPV + Bt Suspension (1 500 mL/hm2) should be applied at the peak of the occurrence of the young larvae of S. frugiperda,and 4：005：00 pm on sunny day to avoid the influence of high temperature and light,so that the virus preparation can play a better role and improve its control effect on S. frugiperda.