Abstract: To evaluate the degradation trend and safety of maleic hydrazide in tobacco leaves,a simple and feasible residue analytical method was established,which was used in the study of digestion dynamics and final residues for 2 years.Maleic hydrazide in tobacco leaf samples was extracted with acid methanol and purified on C18 solid phase extraction column.The results showed that the limit of quantification (LOQ) was 0.1 mg/kg by the determination of high performance liquid chromatography.At spiked levels of 1.0-80.0 mg/kg,the average recoveries ranged from 81.81% to 95.89% for green tobacco leaves and from 82.01% to 83.08% for dried tobacco leaves,with relative standard deviations (RSD) of 2.39%-7.03% and 1.04%-1.71%,respectively.The results of maleic hydrazide degradation dynamic tests showed that the digestion rate in green tobacco was over 90% after 21 days of treatment,with the theoretical half-life being 7.9-9.6 days and the digestion trend was in line with the first order kinetic equation.Maleic hydrazide residues after 7 days of spraying were below the MRL of 80 mg/kg.The residual amount of maleic hydrazide in tobacco was at a lower level of safety risk.