Abstract: The effectiveness of applying TDR technique to measure water content depends on the relationship between the dielectric constant and the water content. The empirical relationship proposed by Topp has been often used in engineering practice. However, the Topp empirical relationship is derived from the test data under the conditions of high salinity and high water content. In this study, a series of tests are performed to investigate the relationship between the dielectric constant and the water content for marine dredged clay with salinity of 1.5%～4.5% and water content of 120%～320%. A new relationship between w/θ and w/k is proposed for the clay with high salinity and high water content. The available data compiled from references are also used to verify the validity of the proposed relationship.