Irregular use of herbicides in rice-tobacco rotation system often leads to phytotoxicity in subsequent tobacco crops.In order to identify the phytotoxicity symptoms of bispyribac-sodium,detect the harmful dose of bispyribac-sodium,and recommend the safe interval period of bispyribac-sodium,the symptoms of bispyribac-sodium phytotoxicity,the influences of bispyribac-sodium on tobacco agronomic and physiological characteristics,and the residual digestion dynamics and harmful dose to tobacco of bispyribac-sodium were systematically studied using field experiment and indoor pot experiment.The results showed that the residual bispyribac-sodium could cause tobacco plants to be short,tobacco leaves to become yellow and curly,and even brown drug spots or wilt and necrosis.In addition,the effect of bispyribac-sodium on agronomic characteristics of tobacco plants deepen with the increase of the dosage and the exposure time.The large inhibitory effect on plant height and leaf area was observed,and the effect was about the same on the 60th day. Moreover,residual bispyribac-sodium disorder the hormone contents in different leaf tissues,in which the contents of IAA and GA₃ were significantly reduced,while ABA content increased in various.The digestion tests showed that when the content of bispyribac-sodium in soil and tobacco leaves was greater than 0. 012 0 mg/kg and 0.018 5 mg/kg,respectively,there would be phytotoxicity on tobacco,and the safety interval period was 85 days. In summary,if the content of bispyribac-sodium in the soil and tobacco leaves was greater than 0. 012 0 mg/kg and 0.018 5 mg/kg,respectively,measures should be taken in time to avoid negative effects on tobacco,meanwhile,the application interval period should be greater than 85 days.