10 deposited layers of ancient floods were found in the profile of Zhongba Cultural Site. They were formed since Middle Holocene, and were submerged by the large flood of 1981 AD. The change in Sichuan Province elevation of these 11 large floods shows an arising tendency and several short-term fluctuation circles in the period. The former reflects the influence of deposition in the river channel since Middle Holocene. The latter reflects the periodical change of Southwest Monsoon intensity reached above the Sichuan basin.