The phenomenon that there exists obvious difference in times of hail shooting between the eastern and western side of the Yachi River is first revealed using observational data,and the difference is found to be associated with down-slope wind,mesoscale leeward slope low-pressure and environment heating.The reason of lake surface high wind and the range-height indicator(RHI) echo character of hail shooting over the Dongfeng lake area at river confluence reaches are analyzed.The echo analysis of the motion and evolution of two hail storms on May 10,2004 in the Yachi River basin shows that storms with multiple convection centers of small scale exhibited different development trends when crossing the river at different river reaches,and hail storms always moved along a route advantageous to their development.This may prove the mechanism for the motion and evolution of hail storms in the Yachi River basin.