Recently, environmental conservation has been considered to be a more important part of the design of irrigation barrages than before. In this study, we investigated the spatial patterns of local flow velocity,etc. in a fishway with orifices (hereafter referred to as “orifice fishway”) to improve the performance for fish migration. The results showed that an orifice fishway enabled to achieve a more convenient maintenance through the use of a short baffle span and to obtain short migration routes for various fish species on a steeper slope of 1:4.5 and with a lower discharge of 0.12 m³/s compared with most of the currently used fishways by the improvement of “partially superimposed orifices”, even if the upstream or downstream water level changed.