Abstract: Aimed to evaluate the safety and regular use of fenoxanil in paddy field,residue decline study of fenoxanil (in fenoxanil and isoprothiolane 35% EC formulation) in paddy plant,water and soil in Zhejiang and Fujian Province were investigated between year 2006 －2007.Results indicated that the linear equation of standard solution was y=246 192x+925.88(r=0.999 7) with the linearity of 0.005 －1 mg/L,the average fortification recoveries varied from 78.6% to 108.4% with relative standard deviation (RSD) of 3.5% －23.4% when fenoxanil was spiked at 0.001 －1 mg/kg(L) level in various matrixes,and the limits of quantification (LOQ) in paddy plant,soil and water were 0.001 mg/kg(L).The decline study of fenoxanil in paddy field was carried out,the decline curves accorded with the first-order kinetics equation,and the half-lives of fenoxanil in paddy plant,soil and water were of 5.2 －9.5,3.8 －7.3 and 0.8 －3.2 d,respectively.