Based on the detection data of CINRAD/SA-D dualpolarization weather radar in Jinan and the field survey data of tornado, the evolution process of radar echo, the structure of tornado cell, mesocyclone (M), tornadic vortex signature (TVS) and tornadic debris signature (TDS) of a class EF3 tornado storm in Gaotang, Liaocheng, Shandong Province, on July 11, 2021, are analyzed. The results show that: (1) The tornado, which was located about 200 km northeast of the surface cyclone centre, occurred under the weather situation of the common effect of the upper cold vortex and the surface cyclone. The two strong convective cells in the spiral convective cloud zone merged and developed into a supercell storm. The downdraft behind the supercell was strong, which together with the strong inflow, induced a strong tornado. (2) The top heights of mesocyclones in storms were mostly between 5 and 7 km; the average maximum shear of mesocyclone before the tornado was 19×10^-3 s^-1; during the tornado maintenance period, the average maximum shear value of mesocyclone reached 51×10^-3 s^-1. (3) The main characteristics of the dual polarization parameters of the bottom layer of the Gaotang tornado vortex were large horizontal polarization reflectivity factor, small or even negative Z_DR and small C_C; the temporal and spatial characteristics of TDS were that the bottom C_C was less than 0.7, the area of the low C_C value area increased significantly with time after the tornado formation, and the bottom C_C value was the minimum, increased gradually with height; the area of the low-value area of C_C was larger in the lower and top layers, and smaller in the middle layer; the maximum height of TDS gradually increased with time after the tornado formation, and the maximum height of TDS reached 4.8 km when the tornado was strongest, and then decreased gradually; after the tornado dissipating, the TDS characteristics above 1.5° disappeared quickly, and the TDS characteristics at 0.5° elevation continued to maintain for about 11 minutes.