The effect of flood discharge by the upstream rivers on tidal dynamic of Power Plant drainage project in Lianyungang is studied in this paper. Firstly, the hydrology environment in the ocean area near the project site is analyzed. Secondly, based on the observed data in 2010, a two-dimensional tidal current numerical model is setted up and fully validated. Thirdly, the effect of flood discharge from the upstream rivers near drainage project on tidal level, current velocity and current field is studied. The results shows that, there are some weak circulating current at flood tide and the current velocity increased by 0.10~1.2m/s at ebb tide at the west of drainage diversion dike. The maximum increased amplitude of tidal level which occurs at 1~2^# units is about 0.12m.