Study on the effects of larval endoparasite Microplitis manilae (Hymenoptera: Braconidae) and Spodoptera exigua Nucleopolyhedrosisvirus (SeNPV) on beet armyworm S. exigua was carried out at the Plant protection Department, College of Agriculture, Can Tho University (T: 24.1 ± 2º C, RH: 78±2%) showed that the second instar larva of S. exigua was the optimum host stage for parasitism of M. manilae wasp with the percentages of parasitism and emergence reached 88.43% and 95.37%, respectively. The parasitoid larvae inside SeNPVinfected hosts were unable emergence despite they could complete their pupation. Furthermore, the weight of the host and the ability to form inclusion bodies of SeNPV were also affected. The weight of parasitized hosts was 9.48mg/larva, was significantly lower than those was both parasitized and SeNPV-infected hosts (from 13.45 to 14.01mg/larva), and those were SeNPV-infected hosts (15.90mg/larva) at 6 days after treatment; the inclusion bodies yield, was 3.49×108 OBs/mL/larva for the SeNPV treatment and 3.01×106 OBs/mL/larva for the both parasitized and SeNPV-infected treatment