Rice leaffolder, Cnaphalocrocis medinalis (Guenée), has become a major pest throughout the rice cultivating areas of China and caused severe damage to rice production.  Cnaphalocrocis medinalis granulovirus (CnmeGV), a naturally occurring baculovirus, is revealed as a potential microbial agent for the pest control.  Field applications of CnmeGV were conducted against rice leaffolder larvae in rice paddies.  CnmeGV infected the larvae not only in the current generation but also in the successive generation, resulting in a sustained infection in the larva population for at least 48 days.  Under diferent concentrations of CnmeGV (7.5×10¹¹ and 1.125×10¹² occlusion body (OB) ha^–1) at 30 days after spraying, larval population reduced up to 76.32% and rice leaf rolled rate kept in 15.42%.  Simultaneously, CnmeGV had no impact on arthropod predators of C. medinalis, with abundances ranging from 2.39 to 3.79 per ten hills.  These results revealed that CnmeGV is suitable as a bio-pesticide for rice leaffolder management in rice paddies.