Abstract: A method for the determination of acid herbicide residues, including halogenated acid herbicides, phenols, nitrogen and sulfur-containing heterocyclic herbicides, was established by changing their existing forms, selection of the derivative reagents and gas chromatography-mass spectrometric (GC-MS) quantitative determination. Under mild reaction condition, the derivative reaction of diazomethane with acid herbicides occurred and produced ester compounds with little by-products, which could be easily detected by GC-MS. By adopting the self-designed diazomethane generating device, the dosage of reaction reagent of diazald was effectively controlled and the harmful gas release was reduced. Experimental comparison was also made between the continuous bubble method and the intermittent bubble method of diazomethane. The detection limits for the herbicides were 4.95~9.80 ng/L and the recovery for different adding levels was 67.5%~126.3% with precision of 1.7%~7.9%RSD(n＝7).