Quinclorac is prone to causing phytotoxicity on tobacco. However, the influence of soil environmental factors on the severity of tobacco phytotoxicity, as well as the remediation mechanism of biochar against such damage, remain unclear. In this study, correlation analysis was conducted between the degree of residual quinclorac-induced tobacco phytotoxicity and soil environmental factors. On this basis, pot experiment and field plot trials were carried out to investigate the remediation effects of different types and amounts of biochar on quinclorac-induced phytotoxicity in tobacco. The results showed that the phytotoxicity degree of tobacco was significantly positively correlated with the residual amount of quinclorac in soil, and significantly negatively correlated with soil organic matter content, while it presented a negative correlation with soil pH and the content of available nitrogen. The appropriate addition of biochar to soil could promote the root growth of tobacco seedlings. In tobacco-planting soil with quinclorac residue of 0.070 2 mg/kg, the application of 1 500 kg/hm2 straw biochar could increase soil pH and organic matter content, reduce the bioavailability of soil quinclorac, alleviate quinclorac phytotoxicity in tobacco, and improve the yield and output value of flue-cured tobacco.