Using Qingdao dual-polarization CINRAD/SA data, sounding and automatic meteorological station data, the polarimetric signatures of a supercell storm occurred in Gaomi, Shandong Province on 3 August 2020 are analyzed. The results show that: (1) The key environmental factors to the development and maintenance of the Gaomi supercell were the strong CAPE, strong low-level vertical wind shear, 200 hPa strong divergence and high humidity. (2) The Z_DR arcs and K_DP high-value areas were important characteristics of the lower layer. The Z_DR arcs matched the high-value region of reflectivity factor gradient on one side of the inflow and correspond to smaller K_DP, which were caused by a few large particles. The K_DP high-value area in the middle of the storm, corresponding to the smaller Z_DR (1-3 dB), larger CC, caused by the high concentration of smaller particles, was the heavy rainfall area. (3) TheZ_DR ring around BWER, corresponding to smaller K_DP, indicate that a small number of large droplets were distributed around BWER. The deep and wide Z_DR and K_DP columns above the BWER indicate that the higher concentration of large droplets was distributed above the BWER. (4) Abundant liquid particles under the -20 ℃ layer and abundant graupel and ice crystal particles above the -20 ℃ layer were the typical vertical characteristics of the microphysics of the Gaomi supercell.