The channel and beach in the mountainous alluvial river are obvious，and shallow and rapid beaches are prone to occur in continuous curved reaches during normal water level and dry seasons. Simple channel dredging for such regulation projects，however，may lead to flow concentrating in channels with higher velocity. To solve the above mentioned problem，we take the third-level channel project of the Xinkaihe beach on Minjiang River as an example to build a fixed-bed physical model for a river of about 10 km. Then，we analyze the riverbed evolution laws，navigation obstruction characteristics，flow characteristics before regulation，and the effects of the channel-regulation design scheme and optimization measures. Moreover，we summarize the regulation principle and scheme of navigation-obstructing shallow and rapid beaches during normal water level and dry seasons. The results show that the longitudinal flow velocity in the channel is less than 3.5 m/s，and the water surface slope is below 2.45‰，which can meet the requirements of channel regulation.