Taking the Lancang River Basin as the study area, the ISIMIP2b protocol having provided four global climate models: GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC5, combining with the VIC model, the ability of simulation, on the extreme value of flood peak and flood volumes (annual maximum flood peak flow, the maximum flood volumes during three days) and extreme floods, was analyzed, in the historical periods (from 1961 to 2005). The changes of average annual runoff volume in the future periods (from 2021 to 2050) compared with the base periods (from 1971 to 2000) under the two scenarios of RCR2.6 and RCP6.0 were also analyzed. Then the P-III distribution curve was combined to predict the intensity of extreme floods in the Lancang River Basin in the future periods. The VIC model can better simulate extreme flood in this basin. The output datas of HadGEM2-ES and MIROC5 climate models have good applicability for runoff simulation in the Lancang River Basin; in the scenario of RCP2.6, the average annual runoff volume in the Lancang River Basin does not change significantly in the future, and may increase slightly, while in the scenario of RCP6.0, the average annual runoff in the future may increase significantly compared with the historical periods; the extreme floods in the Lancang River Basin in the future periods, have no obvious changes under the RCP2.6 scenario. While, under the RCP6.0 scenario, the flood peak and flood volumes are more likely to increase, and frequency and intensity of the extreme floods are also likely to increase.