Abstract: A continuous rainstorm in the eastern Sichuan Basin during Aug 30th to Sept 1th, 2012, is analyzed by using the conventional data, intensive surface observation data and NCEP reanalysis data. The results show that the southwesterly wind speed and the rainfall intensity varied from day and nigh. Southwesterly low- level jet changed similar with southwesterly wind speed at the same time. The diurnal variation of low- level jet causes the same diurnal variation of the vapor, energy and dynamic transport, those caused the rainfall intensity rising in day and falling in night. The vapor, energy and dynamic factors depending on low- level jet mainly concentrates at the 700hPa highly.