Abstract: Field plot trials was conducted to evaluate control efficacy of Bacillus thuringiensis engineered BIOT185 against larvae of Scarab and its ecological safety in peanut field in Dingzhou,Hebei Province.Results showed that the numbers of Scarab decreased by 52.08%-70.51% and the nut-retention rate reached to 50.40%-66.57% after treated by BIOT185 suspension concentration (SC) at 10-fold and 100-fold dilution which showed that high concentrations of BIOT185 SC (100 hundred million/mL) could effectively control larvae of Scarab.The residual numbers of BIOT185 in soil showed downward trend in one year after application,detecting by methods of dull colony notation and PCR.Field investigation showed that the insect population in BIOT185 treated plot was no significant difference with that in control and wild strain HBF-1 and BT185 treated plot.These results demonstrated that engineered strain BIOT185 would not remain in the soil environment,and would not affect insect population in peanut fields.