Taken from the entrance of Juam Dam to 11㎞ long as survey, this study predicted the bed change according to the movement of sediment in jet flow zone. The result of applying compound model and jet model turned out to be satisfactory, though the latter was the better. The jet constant of Juam Dam could be controlled between 0.5 and 0.65. In the jet flow zone of the dam, the prediction of the bed change by the numerical model showed almost the same to the observed data.