Complete Bt cotton system put heavy selection pressure on Lepidoptera insects. Potential development of Bt resistance is major concern over the Bt plant technology. Another emerging problem is the shift of pest status. Those originally secondary pests, such as the tarnished plant bug, have become major problem on Bt cotton. To make transgenic cotton versatile and durable, we investigated several bio-active reagents for synergistic interaction with Bt toxin. Result showed that several bio-active reagents had potential to be used for widening control range and delaying Bt resistance development.