The effects of surfactant sodium dodecylbenzene sulfonate(SDBS) on 24-D adsorption in the soil were determined in laboratory studies.The results showed that at and below the critical micelle concentration(CMC)of SDBS,24-D adsorption in soil was increased,while above the CMC,24-D adsorption was significantly reduced.The effects of the SDBS on 24-D adsorption in soil were caused by several actions.Various hypothesis,based on surfactant properties,were offered to explain the adsorption results.