[Objectives]  Increasing crop damage by Chilo suppressalis (Walker) in recent years poses a major threat to rice production. Due to the resistance of C. suppressalis to multiple pesticides, the parasitic wasp Cotesia chilonis is gradually becoming more popular as a biological control for the larvae of C. suppressalis in the field. The aim of this study was to clarify the ability of insectary-reared C. chilonis to control C. suppressalis in the field, and investigate the effects of various environmentally-friendly pesticides on both C. suppressalis and C. chilonis. [Methods]  The number of dead heart leaves, white ears and dead boot stages of rice, and the number of live C. suppressalis larvae, following releases of two different densities (125 and 250 cocoons) of C. chilonis and seven different pesticide treatments, was quantified and to compared. [Results]  Both densities of C. chilonis reduced C. suppressalis damage to the rice plants; there was no significant difference between the two densities of C. chilonis in this respect, although more C. suppressalis were parasitized after the higher density of C. chilonis were released. Among the different pesticide treatments, cyantraniliprole was the best, followed by chlorantraniliprole, and Bacillus thuringiensis and dimehypo were the worst. There were also large differences in the effectiveness of different doses of cyantraniliprole. The high parasitic rate was found where C. chilonis was released but all pesticide treatments significantly reduced the number of C. suppressalis larvae parasitized by C. chilonis. [Conclusion]  C. chilonis can effectively control C. suppressalis in the field, but the optimal density and methodology of releasing C. chilonis requires further investigation. Although C. suppressalis were parasitized by C. chilonis where the later were released, all seven insecticides tested significantly reduced the proportion of C. suppressalis that were parasitized, indicating that the use of these pesticides is incompatible with the release of C. chilonis as a biological control. The control of C. suppressalis should consider not only the pesticide dosages required to control this pest, but also potential pesticide damage to its natural enemies and the environment as a whole. The results of this experiment provide both a theoretical and practical basis for the subsequent establishment of a more environmentally-friendly strategy for controlling C. suppressalis based on the use of C. chilonis as a biological control.