Abstract: The Diexi earthquake of 7.5 magnitudein 1933 is located at the upstream area of Minjiang River,the east of the Tibetan Plateau. It caused that the rocks at the two sides of the Minjiang River collapsed and blocked Minjiang River,and formed a barrier lake entitled "Diexi Xiaohaizi". After the barrier lake formed,the soil and sand from Songping Valley entered and sunk into the barrier lake successively. It formed gilbert-type fan delta showing threefold subdivision into topset,foreset,and bottomset strata. Songping valley had at least two catastrophic flood events happened according to the landform of the sedimentary bodies and the sedimentary facies characteristics. The study on the deposit characters and causes of Songping ditch accumulation body is combined with flow energy method in dynamics to back calculation. It supplied a new method and thoughts for learning the mountainous geological environment and the occurrence frequency and damage degree of the geological hazard evolution and so on events.