The rapid development of transgenic biotechnology has greatly promoted the breeding of genetically engineered (GE) rice in China, and many GE rice lines are in the pipeline for commercialization. To understand field performances of GE rice, key agronomic traits of two insect-resistant Bt rice lines that have been granted biosafety certificates for commercial production in China were evaluated together with their nontransgenic counterparts under environmental conditions with significant differences in insect pressure. Results from the experiments showed enhanced field performances of the Bt GE rice lines compared with the non-GE counterparts for yield-related traits such as number of panicles and filled seeds per plant, under environmental conditions with no insecticide application. No detectable underlying cost of the Bt transgene was observed in the two insect-resistant GE rice lines, particularly in the GE hybrid rice line. Results further indicated significantly greater yield performances of the two insect-resistant GE rice lines under environmental conditions with non-target insect control compared with no insect control. It is concluded from this study that insect-resistant Bt GE rice, particularly the hybrid line, has great potential to maintain its high yield when ambient insect pressure is high. In addition, proper application of insecticides to control non-target insects will guarantee optimal performance of insect-resistant Bt GE rice.