By examining historical data of Dujiangyan region,this research conducted statistical analysis and wavelet transform to retrieve the ancient flood information in Qing Dynasty,including the grading,frequency and periodicity of flooding as well as climate pattern. Results showed that flooding occurrences amounted to 62 for the whole 268 years of the Qing dynasty,once every 4.3 years,and from early Qing dynasty to the late,flooding occurred with a fluctuated increase trend and obvious periodic pattern: a period of less flooding during 1644 - 1679 and 1790 - 1839,and at high risk of flooding for 1680 - 1789 and 1840 - 1911. Flooding in Dujiangyan region in Qing dynasty obviously existed a short period of 4a and long-term oscillated period of 23a. Besides,there was an 8a in the middle and late Qing dynasty. There were 6 incremental precipitation period in the region during Qing dynasty,occurred in 1744 - 1746,1863 - 1868,1873 - 1875,1878 - 1881,1897 - 1902 and 1906 - 1908 years, respectively,concentrated in the middle and late Qing dynasty. El Nino event was also a major factor inducing flood disasters. It referred to a significant increment of rainfall in the year of catastrophic flood and great flood,with an estimation of precipitation about 1510 mm or more.