To improve the accuracy of the measured relative permittivity based on three-electrode system

a three-dimensional model for relative permittivity measurement is established and solved with consideration of real electrode system’s material properties and dimension by means of the finite element analysis software Comsol for multiple physical fields. In view of the nearly rotational symmetry of the electrodes system

the model is simplified to two-dimensional one to reduce computation amount. Comparison of the computation results between the 3D and 2D models verifies the reliability of the latter. Subsequently

the potential

electric field and surface charge distributions are obtained

and the error of the relative permittivity calculated by the method in a standard is calculated. The influences of sample’s thickness

relative permittivity and area（radius） on the accuracy of the calculated relative permittivity are systematically investigated

and the key factors influencing the accuracy are determined. Employing the 2 D model with the sample’s thickness ranging from 0.2 to 10 mm and relative permittivity ranging from 1 to 100

the errors of relative permittivity are obtained

which are all less than zero. The relationship among sample thickness

measured relative permittivity and real value of relative permittivity is obtained

and the 2 D interpolation method is used to correct the measured relative permittivity. In addition

the proposed correction method is validated by simulation and is applied to relative permittivity measurement of an insulating material.