Remediation of soil contaminated by hydrophobic organic compounds using biosurfactants as additives involves interactions between soil matrix, hydrophobic organic compound contaminants, biosurfactants and microorganisms. In this paper, the mechanism for biosurfactants to enhance the contaminant degradation is basically revealed. Biosurfactants can enhance solubilization of the contaminants in the soil matrix, change their mass transfer properties into the aqueous phase, as well as affect their sorption properties. Furthermore, biosurfactants can act on microorganisms and change their surface properties, accordingly cause new growth and uptake behavior of the bacteria in the soil matrix. Both the physicochemical and the microbiological effects can basically increase the bioavailability of the contaminants and enhance their degradation.