Abstract: Thuringiensin, a bio-product of Bacillus thuringiensis isolate CT 43, was t ested for its effect on the predation of the newly hatched nymph Orius sauteri to Tetranychus urtiae eggs using in the quadratic optimum regression desi gn. The elationship between the day average numbers of preys (y) and the number of preys(y) and the number of preys (x ₁) and predators (x ₂) was found to fal l into the following models: Y treatment =-0.0021(x ₁) ²+1.2112(x ₂) ²+0.8822x ₁-10.3465x ₂ -0.0649x ₁x ₂+1.7174 Y control =-0.0017(x ₁) ²+0.7734(x ₂) ²+0.694x ₁-6.4914x ₂-0.0474x ₁x ₂-0.4636 The qualitative and quantitative analysis indicated that the predation capacity of O.sauteri to T.urticae eggs was weakened when the newly hatched nymp h were treated by thuringiensin, but the impact wa not significant compared with the control. This result showed that thuringiensin could be considered as an ef fective control agent of two spotted spider mite and relative safe to O. saut eri.