We calculated the field similarity,field amplitude ratio,the day,the kinetic energy intensity of monsoon component and the degree of abruptness for every year in South China Sea summer monsoon region.The presage day of summer monsoon in South China Sea region for each year can be determined by the similarity and amplitude ratio.There are minimum of the absolute value of similarity,maximum of the similarity variability and minimum of the kinetic energy of flow field at the presage day.For most years the presage day is a slightly earlier than the onset day determined by the conventional synoptic-climatological method.The of summer monsoon in South China Sea region is characterized by the abrupt change of flow field in most years,but a few years characterized by harmonic change(no abrupt transition).The kinetic energy intensity index reflects the intensity of monsoon after in South China Sea region. The presage day and the kinetic energy intensity index and the abruptness undergo pronounced inter-annual and inter-decadal variability.