We have studied the function of a series of sabo dams on sediment runoff control using a numerical simulationm ethod of one dimensionabl ed variation.A closedt ype dam, a verticals lit dam, and a horizontals lit dam are taken up as sabo dams and five dams of each type were placed at an interval of 400m in a river. First of all, the applicabilityo f the simulationm ethod to the sedimentd epositionp rocess and the erosionp rocess in the upstream reach of a dam was verified. Next, the bed variation was calculated for the riverbed of sediment mixture not covered by armor coat. The second to the fifth sabo dam was filled up with the sediment eroded in the reach between the dam and the upper dam while the upper dam was trapping the sediment. Therefore, they could not have a storage capacity enough to reduce the amount of runoff sediment. On the other hand, a series of sabod ams in the riverbedc overedb y armor coat couldc ompletelyt rapr unoff sedimentt o be controlled.