The dielectric constant is an important parameter that affects the performance of high-frequency substrate, and the accuracy and spatial distribution of the dielectric constant of the substrate will have an important impact on the performance of microwave circuits. In this paper, the resonant ring circuit of enhanced coupling ring, shielded through hole and coplanar waveguide technology is designed first, to enhance the anti-interference ability of the ring to the outside world, and to distribute S21 between -30 to 20 dB, and improve the transmission efficiency. Secondly, the influence of different ring average radius, ring width and coupling gap on the simulation results is analyzed. Then, the resonant ring circuit is processed and tested. The measured results show that the dielectric constant error is less than ±0. 007 at the frequency points of 2, 10 and 24 GHz, which proves that the method has high test accuracy. Finally, based on the test and analysis of the dielectric constant distribution of a domestic substrate based on the resonant ring circuit, the results show that the dielectric constant error caused by processing and the spatial distribution of the substrate is less than ± 0. 024, which proves that the substrate has good performance.