Artificial feeding and bioassay methods of Batocera horsfieldi(Hope) adults had been applied in laboratory, and the insecticidal activity of Bacillus thuringiensis（Bt）to B.horsfieldi had been determined. The result indicated that Bt had obvious poison effect against B.horsfieldi. The B.horsfieldi adults were fed with Rosa multiflora Thunb.branches whose surfaces were smeared with Bt liquid. The death rates, body mass changes and eggs quantities of B.horsfieldi adults were regularly analyzed. Through one primary screening and twice rescreenings, the insecticidal activity of 80 Bt strains to B.horsfieldi adults was determined in laboratory, and the best strain was ZQ-51 which had the most powerful toxicity to adults. In the treatment of strain ZQ-51, the mean mortality was 53.33%, the mean reduction in mass rate was 5.67%, and the mean reduction in hatching eggs rate was 12.48%. These were remarkably different from those of the control group. This strain had been isolated from intestinal tract of infected dead B.horsfieldi again, and was similar with strain ZQ-51 in morphologic characteristics and insecticidal activity, which proved that the toxicity to B.horsfieldi could develop after their intestinal tracts infected with Bt strains. 