Nontarget impacts of six transgenic Bt rice lines (expressing the Cry1Ab or Cry1Ab/Cry1Ac protein) on the thrips, Stenchaetothrips biformis (Bagnall), attacking the rice seedling and tillering stages, were evaluated under laboratory and field conditions. Laboratory results showed relatively longer larval, pupal development and preoviposition durations of S. biformis. Although it had a shorter oviposition period, female adult longevity and less total laid eggs were found when fed on some tested Bt rice in comparison to non-Bt controls. S. biformis population dynamics in Bt and non-Bt plots were monitored using the plastic bag and beat plate methods. In the field, the temporal patterns of S. biformis population changes were similar between tested Bt rice lines and their respective control; however, the total number of S. biformis individuals collected from the Bt plots were significantly less or the same, varying from variety to variety, compared with those from the non-Bt plots. ELISA results showed that the Bt insecticidal protein could be transferred from Bt rice to the thrips, and the concentrations of the protein in rice leaves and thrips were not significantly correlated with some important biological parameters of the thrip. In addition, the potential effects of Bt rice on the abundance of S. biformis candidate predators are also discussed. In conclusion, our results show that the six Bt rice lines assessed may be less preferable host plants to S. biformis at the individual and population levels in comparison to the non-Bt rice plants.