Abstract: A simple,sensitive and selective method using gas chromatorgaphy equipped with flame photometric detector (GC-FPD) was developed to determine residues of glyphosate-ammonium in soil and ramie root.Soil samples were extracted with 0.01 mol/L sodium hydroxide and other samples were extracted with water and acetone.Glyphosate was previously derived with trimethylorthoacetate (TMOA) in the presence of acetic acid.Combination of AG1-X8 anion exchange chromatography with Florisil cartridge cleanup process was favorable for the GC-PFPD analysis.The recovery ranged from 73.6% to 102.6% and 85.9% to 105.1% with the relative standard deviations of 2.3% to 8.1% and 5.4% to 13.0%,respectively.The limit of detection (LOD) of the method was 0.5×10-10 g.The limit of quantification (LOQ) was 0.05 mg/kg.The half-life of glyphosate-ammonium was 1.6-2.6 d,1.0-1.8 d and 1.1-1.5 d in soil of Hunan,Guangxi and Fujian Province at two years,respectively.No glyphosate-ammonium residues were detected in ramie and soil samples at treatments of 2 250-3 375 g(a.i.)/ha at harvest season (60 days after the treatment).