A statistical analysis is done for Meiyu heavy rainfall over Changjiang-Huaihe valleys during 2007—2011 based on the daily precipitation data.It has been verified that there are two separate heavy rainfall regions over Changjiang and Huaihe valleys according to the rainfall frequency and distribution during Meiyu season.The two rainfall regions have their different features at prevailing meso-system,space structure,Meiyu front location,moisture transportation channel,rainstorm position,dry and cold air intrusion,southward movement of dry-cold momentum,etc.Under dominated dynamic circulations at high level,more low vortex heavy rainfall(77%) happened over Changjiang valley and more convergence line heavy rainfall(86%) happened over Huaihe valley.The prevailing shallow meso-systems cause the characteristics of Meiyu heavy rainfall with strong rainfall and weak wind.The low vortex over Changjiang valley brings moisture from both South Sea and East Sea,so it makes the heavy rainfall with a larger and wider covering area in Changjiang valley than that in Hauaihe valley.The convergence line in Hauaihe valley brings moisture from only South Sea.The dense zone of the potential pseudo-equivalent temperature isoline presents the Meiyu front and the leading edge of the dry and cold air,with an abrupt shape for the convergence line structure in Huaihe valley but a dry and moisture overlapped shape for the low vortex structure in Changjiang valley.On the north side of Meiyu front,the dry-cold intrusions from mid-high troposphere are downward,with a lower center position and a larger size in Changjiang valley than in Huaihe valley.The vertical distribution of moist potential vorticity shows that the heavy rainfall area is under the baroclinic part of moisture potential vorticity more than 0,a positive vorticity development area.The dry and cold momentum is presented by the baroclinic part of moisture potential vorticity less than 0,its centre transports downward and southward,and its south edge has indicative function to the position of heavy rainfall.The latitude effect and cold air density cause bigger southward velocity component of the dry and cold air mass momentum in Changjiang valley than in Huaihe valley.The combined effect of several influence factors(excluding the terrain factor) is benefit to the separation of heavy rainfall in Changjiang and huaihe valleys.