Flood in Vu Gia - Thu Bon basin is quite complex because of the combination of cold air and typhoon operations causing heavy rainfall on a large scale. In addition, the topography is steep so flood occurs more and more fierce and cause serious damage to people and property. This paper researched and constructed mathematical model (including the combination with hydrological and hydraulic models and meteorological forecasting model, such as MIKE NAM, MIKE 11, HECRESSIM and HRM to serve the flood forecasting for the basin). Besides, the paper is also successful for building two plan with the estimated time (18h and 24h, respectively) to forecas at the downstream stations (as: Ai Nghia, Giao Thuy). Trial results forecasting were good with ensuring level from 0.6 to over 0.82 in 2010.