By using the NCEP reanalysed data，the conventional observation data and Doppler radar data of the synoptic and mesoscale characteristics of t wo strong convective weather in Hexi Corridor are analyzed. The results show tha t they are differ greatly from each other on the circulation and mesoscale syste m. A rightmoving squallline(cyclone) led to the hail on 7 July 2006. In cont rast, a stong leftmoving (anticyclone) supercell brought on the hail on 10 Aug ust 2006. The value of stormrelative helicity(SRH) for rightmoving squalll ine is positive in the 0-3km layer, while the value of stormrelative helicity (SRH) for leftmoving supercell is negative during development.