[ Objective ] The paper was to screen intestinal aerobic bacteria from 2nd instar larvae of Dendrolimu kikuchii and determine its toxicity. [ Method ] The intestinal samples of 2nd instar larvae of D. kikuchii were diluted in gredient and coated on plates to isolate strains, and a total of 5 strains of aerobic bacteria were isolated. With bacterial genomic DNA as template, the universal primers of bacterial 16S rDNA （27f and 1 492r） were used to amplify the template, 4 restriction enzymes Hae Ⅲ and Hind Ⅲ, Hinf Ⅰ and Taq Ⅰ were used to carry out ARDRA polymorphism analysis on PCR products. [ Result] Clustering map analysis showed that 5 strains of aerobic bacteria clustered into two different taxonomic operating units （OTU） in 95% similarity level, this indicated that the genetic diversity level of intestinal aerobic bacteria in 2nd instar larvae of D. kikuchii was relatively low. The indoor toxicity test showed that the death peaks of insects killed by intestinal bacteria were during 4 - 10 d, the insecticidal effect of strain 4 was the best with corrected mortality rate of 53.57% at 12 d. [ Conclusion] The paper provided reference for control of D. kikuchii.
