In the upper part of the river in mountainous area, discharge changes violently so that a lot of floodwood and sediment moved heavily. In order to save the function of Fishway in the Sabo Dam in this river, we developed the method of controlling discharge at the inflow section. The method is consist of the orifice and the overflow weir which is our suggested structure. In order to estimate the function of the combination of the orifice and the overflow weir, the hydraulic test was held at the actual Sabo Dam. As a result of this study, we confirmed the structure controls discharge at the inflow section appropriately.