The pharmacokinetics of difloxacin（DIF） and its metabolite sarafloxacin（SAR） in hemolymph,muscle,hepatopancreas,spermary and ovary of Chinese Mitten-handed Crab（Eriocheir sinensis） were studied by RP-HPLC,after administration by single oral garage of 20 mg/kg.The concentrations versus time in hemolymph,muscle,hepatopancreas,spermary and ovary of E.sinensis were well described by a two-department open model.The results of present studies showed that DIF was rapidly absorbed and extensively distributed in E.sinensis.The apparent volume of distribution（V_d） of DIF of hemolymph,muscle,hepatopancreas,spermary and ovary was 3.170 L/kg,2.122 L/kg,1.045 L/kg,1.051 L/kg and 0.203 L/kg respectively.DIF eliminated slowly.The elimination half-time（t_1/2β） was 96.316 h,88.228 h,137.524 h,67.021 h and 124.679 h,respectively,and the total body clearance（CL_s） was 0.783 L/h·kg,0.04 L/h·kg,0.013 L/h·kg,0.011 L/h·kg and 0.008 L/h·kg.The metabolite SAR concentration-time profiles of the hemolymph,muscle,hepatopancreas,spermary and ovary presented similar trend.The multipeak phenomenon were observed,but the peak time of the metabolite SAR in hemolymph,muscle,hepatopancreas,spermary and ovary was the time that the eliminating rate of DIF was very low.Considering that the eliminating rate of DIF and metabolite SAR were very low.Withdrawal time was more 24 d when the maximum residue of DIF is 100 μg/kg and of SAR is 30 μg/kg after single oral administration of DIF in E.sinensis.