Based on the hydrographic data analysis, 2D modeling and fluvial evolution analysis which are combined to study the main changes of hydrodynamic and features of fluvial evolution, we can get that the water level change is the direct response to the lowering of riverbed in the runoff dominant reaches while it is controlled by the tidal dynamic in the tide affected reaches during the median and lower water level. The tidal change is the response to the lowering of riverbed, deceasing of the bottom slope and increasing of the channel capacity. The velocity change is the response to the water depth and longitudinal slope.