Based on the NCEP/NCAR reanalysis data,the FY2E-TBB data and the precipitation observed by meteorological stations,the general circulation and precipitation before and after South China Sea(SCS) summer monsoon onset of 2011 are analyzed.Results show that the convective activity first appears in the Bengal Bay,then extends to SCS in 2011.Meanwhile,South Asia high moves to the northern Indo-China peninsula and the western Pacific subtropical high withdraws eastward from SCS,and SCS summer monsoon breaks out in the fourth pentad of May(the 28th pentad of 2011).After the monsoon onset,the India-Bengal Bay summer monsoon trough forms,and the southwest flow prevails in lower troposphere over most of SCS,coupling with abrupt changes of both the convective rainfall and the circulation over SCS.With the progress of monsoon activity,the rainbelt moves northward and the great precipitation appears over the middle and lower reaches of the Yangtze River where the rainy season begins.It is found that both the SCS summer monsoon and the Meiyu over the middle and lower reaches of the Yangtze River are influenced by the subtropical high.There is an obvious negative correlation between intensity of Meiyu over the middle and lower reaches of the Yangtze River and that of SCS summer monsoon,but there is a remarkable positive correlation between onset time of the Meiyu and that of SCS summer monsoon.SCS summer monsoon is weaker and its onset time is earlier,while Meiyu precipitation over the middle and lower reaches of the Yangtze River is heavier and its onset time is earlier in 2011.