Abstract: Based on the relationship between monthly mean discharges and maximum flood peaks,a flood frequency assessment model is established,and nonparametric method is used to estimate the conditional probabilities of each discharge class.Using the monthly water balance model,the sensitivity of flood frequencies and discharge peaks for changing climate conditions have been analyzed and tested.The results indicate that flood frequencies and peak discharge are more sensitive to precipitation variation than to the temperature increase.In Dongjiang and Hanjiang river basins,temperature incerase 2℃ and rainfall changes between plus 10%-20%,the occurrence of a two-year flood frequency will increase from 19.1% to 47.4%,annual maximum peak discharge which return period is 20 years will increase from 10.2%to 24.1%.