On the basis of linear regression, Mann-Kendall Method, the Z-test method and commensurability, by using yearly precipitation data from 46 meteorological stations from 1960 to 2012 on the southeast coast of China, spatio-temporal characteristics of precipitation and flooding tendency for the southeast coast of China were investigated. Results indicate that 1) precipitation of the southeast coast of China has an increasing trend and the increasing rate is 19.1mm/10a; 2) precipitation has a decreasing trend in high precipitation regions but an increasing trend in low precipitation regions. Most of the regions, where precipitation has a decreasing trend, are high precipitation regions, and meteorological stations, where precipitation has a decreasing trend from south to north. Risk of regional flooding disasters is increasing gradually; 3) droughts and floods have an obviously inter-annually changing trend. It was the droughts period from 1960s to 1970s. Flooding has increased annually from 1980s to 1990s. Droughts and floods disasters happened frequently after 2000; and 4) time series of severe droughts have a distinctive symmetric structure. Via commensurability, map of butterfly structure (MBS) and commensurable structure, we claim that flooding would happen again in 2016 on the southeast coast of China.