The effect of Aphid gossypii Glover feeding on the transgenic cotton varieties GK12，33B and SGK321 and conventional cotton varieties Simian3，33 and Shiyuan321，on the predatory behavior of Propylaea japonica Thunberglarvae was investigated． The results show that the relative biomass ofP． japonica toA． gossypii was higher on transgenic cotton than on conventional cotton and that the number ofP． japonicaincreased with prey density． MoreA． gossypii were preyed on by 1 ^st and 2 ^nd instar larvae ofP． japonicaon SGK321 than on GK12 and 33B． Conversely，moreA． gossypii were preyed on by 3 ^rd and 4 ^th instar larvae ofP． japonicaon GK12 and 33B plants than on SGK321 plants． The predatory responses ofP． japonica toA． gossypii feeding on transgenic cotton fitted the Holling－Ⅱequation． The maximum daily predation rate of 1 ^{st ． japonica larvae onA． gossypii was higher on GK 12 and SGK321 plants than on controlplants and processing time was shorter than on control plants． The maximum daily predation rate of 2nd ． japonicalarvae was higher on 33B and SGK321 plants and processing time was shorter compared to control plants． The maximum daily predation rates of 4and 3 rd instarP}instarP^th instar larvae on all three transgenic cotton varieties were greater than those of larvae on control plants，and processing time was shorter than on control plants． In addition，the maximum daily predation rate ofP． japonicaon the dual toxin transgenic cotton SGK321 was less than that on the single toxin varieties GK12 and 33B．