Based on Xishui dual-polarization radar detection data, a hailstorm and short-term severe rainfall occurred in northwestern Guizhou on May 2, 2021 were analyzed. The results show that the hail and short-term severe rainfall can be identified by dual-polarization radar well. We analyze the hail phase state evolution. The obvious hail features (differential reflectivity Zdr and specific differential phase Kdp < 0, co-polar correlation coefficient CC is 0.9～0.95) occurs at high level. As the height decreases, the values of Zdr and Kdp change from negative to positive and CC increased to about 0.95, which indicate that the hails melt into big raindrops or outsourcing water film hails. This is consistent with the ground observation facts. CC hole, Zdr and Kdp columns, three-body scatter signature are observed, which can indicate the hailstorm evolution. Zdr and Kdp of short-term severe rainfall increase with the intensity of reflectivity, and the value of CC is above 0.95. The large Kdp value can indicate short-term severe rainfall location well.