Abstract: Climatic change is increasingly concerned. The observed and investigated rainfall and the discharge data from 20000 rainfall stations and 175 hydrologic stations on large and medium rivers in the recent 100 years(especially 50 years)of the 20th century are used to study the inter-decadal change of the extreme values of rainstorm and flood in China(mainly in exorheric basins). These studies include the decadal mean changes of rainstorms of the long series stations,contrasting the early years,mean value of the point rainstorm's extreme values with that of the recent 50 years,the decadal distribution of the maximum point rainfalls and the decadal distribution of extraordinary flood peaks. The extreme values of rainstorm and flood varying with decades are analysed from the different durations and regions;the variable facts are demonstrated;some decadal ratios are calculated;and several affecting factors are investigated.