Abstract: Field experiments were carried out in Jinan and Hangzhou and laboratory analysis performed to determine dynamics of fenpyroximate residue in cotton leaves,cotton seeds and soil,using liquid extraction method and HPLC method.Results show that the lowest detectable limit of the method was 0.01 mg·kg^-1(S/N=3).When the pesticide was applied at a rate of 0.10,0.50,1.00 mg·kg^-1,its recovery rate varied in the range of 72.5%～103.1%.Degradation of fenpyroximate in cotton fields in Jinan and Hangzhou demonstrated a similar trend.The half-life of fenpyroximate in cotton leaves was in the range from 3.8 to 4.3 days,and in soil from 8.8 to 9.6 days.The final residue of fenpyroximate was <0.01 mg·kg^-1 in cotton seeds,and <0.01 to 0.98 mg·kg-1 in soil.It is,therefore,suggested that the MRL(maximum residue level) of fenpyroximate in cotton seeds be set at 0.1 mg·kg^-1.