Using ground based microwave radiometer observation data, two hailstorm cases that happened in Xianning of Hubei Province on 26 February 2009 and 12 April 2010 are analyzed. The results show that low level warm air transportation and mid level dry cold air intrusion contributes to the “upper dry and lower wet” 2 layer vertical structure of 0-10 km relative humidity. The updraft transports upward sensible heat and latent heat of the low level, resulting in the significant warming of 2-3 km layer, and the slight rising of 0, -5 and -20℃ layers. As the low level moisture is rising up, ILW, IWV and super cooled water grow rapidly before the hail. After the wet vapor goes through the cold layer, the ice crystals increase. When the ice crystals increase and fall into the area above 0℃ melting layer, the ice crystals are melted, leading to an increase in liquid water, and part of the water becomes hails or surface precipitation, so that the ILW, IWV and liquid water content below 0℃ decrease after hails. The above conclusion is of some significance to the early warning of hails.