Research on water resource forecasting and predicti on is the main base work for water resources optimum allocation and sustainable utilization. The water resource prediction model over Hanjiang River basin was built based on Mike Basin program, in which the rainfall and runoff processes of every subbasin were simulated by the NAM model. And some key elements of the model were researched in detail. The result indicated that by means of refining model dividing, enhancing the accuracy of parameter calibration, and promoting the handling way to the reservoir, the accuracy of the forecasting model can be obviously enhanced.