[Purposes] The paper aims to establish the relationship between the dielectric constant of coarse?grained soil and matric suction, the water content of coarse?grained soil is then determined based on the dielectric constant. [Methods] Firstly, the dielectric constant and matric suction of different coarse?grained soils were obtained by dielectric constant tester and filter paper test. The relationship between them was analyzed, and the suction dielectric characteristic curve (SDCC) model was established. Then, the percent fines content (P) of each coarse?grained soil was determined by a laser particle size analyzer, and the soil water characteristic curve (SWCC) of each coarse?grained soil was obtained by combining the filter paper test results and the FREDLUND & XING's model. Finally, P was used to predict the model parameters of coarse?grained soil's SDCC, and the relationship between SDCC and SWCC was established. [Findings] The SDCC mechanical empirical model of coarse?grained soil is proposed to establish the direct relationship between the dielectric constant of coarse?grained soil and the matrix suction. The relationship between the P and the parameters of the SDCC model is obtained by fitting. The parameters of the SWCC model can also be estimated by the P. Finally, the interdependence of dielectric constant?matrix suction?water content is established. [Conclusions] There is a relationship between matric suction and dielectric constant of coarse?grained soil. The parameters of SDCC and SWCC can be estimated by using the P. The matric suction and water content of coarse?grained soil can be determined by testing P and dielectric constant of coarse?grained soil.