By consulting the channel map of Yibin-Chongqing section in the upper reaches of the Yangtze River，this paper counts the morphological parameters such as the height of straight side beach and the ratio of beach width to channel width under the condition of dry water level，and designs two kinds of water surface slopes（α= 0.167 and 0.200），the variation laws of water depth and velocity of main sections under different hydraulic conditions are studied by using generalized model test. The results show that the water depth is the main factor affecting the change of water depth difference and velocity at the same measuring point of the main section，that is，the closer the distance to the beachhead，the more obvious the backwater phenomenon，the increase of water depth，the weakening of turbulence，and the smaller the change of water depth difference at the same measuring point. When the flow and other hydraulic conditions are the same，the water depth increases，the turbulence decreases，and the changes of vertical average velocity，near bottom average velocity and section average velocity along the section decrease accordingly. The research results will provide a reference for the flow characteristics and evolution mechanism of the staggered beach.