Abstract: By using batch adsorption method,adsorption isotherms of two nonionic surfactants (Brij30,Tween-80) in two sediments were investigated and parathion-me thyl adsorption behavior between the sediments and water with or without Brij30 or Tween-80 compared.Results show that the S-model is appropriate for describing adsorption isotherms of Brij30 and Tween-80 in sediments.Adsorptions of Brij30 and Tween-80 are the results of their adherence or aggregation on sediment mineral matter and partitioning in sediment organic matter.When Brij30,Tween-80 concentrations are lower than CMC,parathion-methyl adsorption on sediments decreases as Brij30 and Tween-80 molecules compete against parathion-methyl molecules for adsorbent bit attainment.However,because Brij30 and Tween-80 surface micelle in the two sediments adsorbs parathion-methyl and surfactants disperse the sediment colloids,the adsorption of parathion-methyl to sediments increases as Brij30,Tween-80 concentrations are higher than CMC.