Abstract: A GC method was used to determine degradation behavior and evaluate environmental safety of diquat in sugarcane and soils in Hunan and Hainan.Results show that the half-life of diquat in sugarcane and soil was 4.72 and 50.59 d,respectively,in Hunan,and 5.73 and 40.01 d,respectively,in Hainan.When diquat was applied at a recommended rate,residue of the effective component was much lower than 0.05 mg·kg-1,which ensures food safety of sugarcane.