Abstract: The influences of the Tibetan Plateau on weather anomalies over the Chang jiang River in 1998 are studied by analyzing the NCEP reanalysis data.There are many short wave troughs over the baroclinic zone,nort heast part of Tibet an Plateau,associated with it sthermal effects.The short wave troughs pass through the Meiyu frontal zones and reinforce them,finaly cause the heavy rainfall.The 8 flood peaks in middle reaches of the Changjiang River are caused by short wave troughs moving eastward.The relation between the heavy rainfall during the second period of Meiyu rainfall and the severe flood is also discussed.Several heavy rainf alls prior to the last one saturated soil moisture,So the severe floods are easily followed the last heavy rainfall which offered a chance for confluence of high-stage waters from the upper reaches of the Chang jiang River and from the Dongting and Boyang Lakes.