Based on the S-band dual-polarization Doppler weather radar data in Jinan, sounding data and surface meteorological observations, the dual-polarization characteristics of the evolution of two severe storms, namely the squall line on 30 June and the supercell on 9 July 2021, are analyzed. The results are outlined below. (1) The two severe storms both occur in the synoptic situation of cold vortex, and their trigger mechanisms and morphological structures are different. The supercell storm is triggered by the gust front on 9 July, while the strong squall line is triggered by the weak cold front on 30 June. (2) The continuous stimulating, merging and developing of new convective cells result in the two severe storms lasting for a long time. (3) The stimulation of new cells in the intersection area of the gust front and the right side of supercell causes the storm to propagate rightward, so the right side of the supercell storm is the key area. The continuous stimulation of convective cells ahead of the east side of the strong squall line guides the storm to rapidly propagate, move forward, and evolve into bow echoes, so the key area is the front of the squall line’s left side. (4) At the initial moment of the new cells (30-44 d_BZ), the differential reflectivity (Z_DR) columns can reach the height of -10 ℃, containing a few medium sized raindrops. With the rapid development of new cells, Z_DR columns can extend to the height of -20 ℃ or even higher, containing a small amount of large liquid raindrops or small melted ice particles. (5) The main characteristic of the cell merging is the merging of Z_DR columns, that is, the merging of the updraft zones. After merging, the width or height of Z_DR columns and the values of Z_DR and K_DP increase, and the size and concentration of liquid particles in the strong updraft zone grow larger obviously. There are extra-large raindrops with the diameter exceeding 5 mm or melted ice particles equivalent to extra-large raindrops inside Z_DR columns.