To assess effects of Bt rice expressing a synthetic Cry1Ac1 gene for control Cnaphalocrocis medinalis (Guenee) (Lepidoptera: Pyralidae), we conducted laboratory tests to evaluate the potential impacts of Bt rice on non-target herbivore, non-target pollen-feeder and non-target predator. Also we investigated the community structure of arthropods in Bt and non-Bt rice fields during the rice-growing season in 2007 and 2008. There were no significant differences in development, survival and emergence of non-target herbivores, non-target pollen-feeder and non-target predators between Bt and non-Bt rice although tibia length of non-target predators with BPH feeding on Bt rice showed significantly longer than in non-Bt rice. In 2-year field study, a total of 43 familes in 10 orders were identified from 64,099 collected insects and a total of 29 species in 23 genera and 9 families were identified from 4,937 collected spiders. Abundance, Shannon’s index and family richness in insects and species richness in spiders were very similar between Bt and non-Bt rice for 2 years and there was no significant difference. The results indicated that the transgenic Cry1Ac rice tested in this study had no adverse effects on the rice insect and spider community structure in field condition and on the development, survival, emergence and adult fitness parameter of non-target arthropods in the laboratory conditions.