Abstract: Both runoff and tide act on the flow in tidal reach.Sea level rising will lead to increase of tide-generating force, in turn, the impact on the flow in tidal reach.The hydrodynamic model for lower reaches of Yangtze River is built with MIKE12 and the change of tidal wave in the tidal reach from Wuhu to the estuary of the Yangtze River are calculated according to the runoff data from Datong Hydrometric Station, for sea level rising of 0.5m, 1m, and 2m, respectively.The findings of the research are presented as follows:1.The tidal reach can be divided into two sections in terms of the impact of sea level rising, one from the estuary to 35km upstream of Xuliujing and the other from 35km upstream of Xuliujing to the tidal current limit.2.For sea level rising of 0.5m, 1.0m, and 2.0m, the increase of the average tide level in the affected section is notably less than the increment of sea level, depending on the runoff and the position.The impact goes down when going upstream and/or as runoff increases.3.The change of tidal range and the change of sea level are positively correlated.The runoff has strong influence in upstream section but little influence in the estuary.Speed of tidal current in the reach goes up as sea level rises.The strength of runoff will decide the affecting range of tidal current.