Abstract: It is of great significance to the study of ionic contamination that the electrical conductivity of pore fluid in saturated sandy soil reflects the ion content. The electrical conductivity of pore fluid in saturated sandy soil has a perfect linear relationship with the bulk electrical conductivity of the soil, which confirms the Archie’s law. The values of the exponent, m, in Archie’s law for saturated sandy soils are obtained, and a new method is developed based on the use of TDR technology to monitor the change of the electrical conductivity of pore fluid in saturated sandy soil. The experimental results show that TDR is able to provide a reasonably accurate estimation of the electrical conductivity of the pore water. It is of great importance to monitor the ionic contamination in saturated sandy soils in situ.