Abstract: This paper analyzed the variations of meteorological elements during the flood season (May to September), by using the daily and monthly precipitation and NCEP reanalysis data from 1980~2010 from the 7 meteorological stations in Changdu. The results show that there is distinguished difference of precipitation during the flood season in Changdu between different stages of an El Nino-Southern Oscillation (NESO) event. The precipitation has reduced during the development stage of ENSO in the flood season in Changdu, except for Basu station. The variations of numbers of days with precipitations are contributed to monthly precipitation. The number of days of moderate and heavy rain increased in the months when the precipitation is high, whereas the number of days of moderate and light rain decreased in the months when the precipitation is low.The low precipitation is mainly caused by the South Asia high exhibiting the east, by comparing the atmospheric circulation between the regular year and the year with ENSO