Abstract: The damage caused byApocheim ia cinerarius E rscho ff and Orthosia incertaH ufnage in B t transformedP op ulus nigra p lantation located inM anasi P lain Forest S tation, X injiang Uygur Autonomous Reg ion w as investigatedduring 1997- 2001. The leaf loss w as less than 10% and the larvae density in the so il decreased from 18 headsm-2 in 1997 to 8 heads m-2 in 2001, but the larvae density increased in the non-transgen ic p lantation. In 2005,the leaf loss caused by Apocheim ia cinerarius E rschoff in B t transformed plantation in Huairou o f Beijing w as lessthan 20% , but itw as 90% in non-transgenic pop lar p lantation. This indicated that the insect-resistance of transgenic pop larw as stable, and can reduce the larvae density effective ly in the field formany years. The variety, numberand parasit ic rat io of the natural enem ies o f insects in the transgenic pop lar plantation (M anasi) w ere mo re thanthose in the non-transgenic pop lar plantations. The resu lt of the inocu lation of the insect pupae co llected from transgenic poplar p lantat ion, nearby poplar p lantat ion and the contro l p lantation w ith the w asp (Chouioia cunea Y ang. )show ed that there w as no significant d ifference o f thew asp ec losion rate and number betw een them. It can be concluded that up to know there is no significan t negative effect o f transgen ic pop lar on the natural enem ies o f insects.