Abstract: The bioassay and field evaluation of acetamiprid against rice stem borers were carried out. The results showed that:1) Acetamiprid had excellent systemic toxicity against Scirpophaga incertulas and Chilo suppessalis, the mortality of Chilo suppessalis with 25 mg/L acetamiprid was 90%, and that of Scirpophaga incertulas with 100 mg/L acetamiprid was 92.3%. 2)The medial lethal dosages(LD 50) of acetamiprid against Scirpophaga incertulas and Chilo suppessalis were 0.6400 and 0.2130×10 -4 μg per individual, respectively, while that of methamidophos were 13.3114 and 17.8114×10 -4 μg per individual,respectively. 3) The integrated efficacy was more than 85% with 20 mg/L acetamiprid against Chilo suppessalis and 25 mg/L against Scirpophaga incertulas. 4) The efficacy of 200 mg/L and 500 mg/L acetamiprid on eggs of Chilo suppessalis and Scirpophaga incertulas were 83.4% and 93.4%, respectively . 5) Plot experiment in paddies showed that application of 112.5 and 300 g/hm 2(a.i.) acetamiprid could control dead heart and white head engendered by Scirpophaga incertulas in Jiangsu Gaochun, respectively, and 67.5 g/hm 2 could control white head in Jiangsu Rudong. 112.5 g/hm 2 acetamiprid was also effective for control of Nilaparvata lugens. 6) Acetamiprid was safe to enemies in field.