The author of this paper analyzed the environmental impacts of building sluice on the river estuary of Zhejiang Province. The results show that building sluice on river estuary has such positive effects as controlling flood, resisting tide，increasing the amount of available water resources, improving the navigation conditions of inner river, better the city water environment landscape, etc. But in the meantime it can bring about some negative effects such as sediment accumulation in estuary area, reduction of regional drainage capacity, degradation of water quality, damage of the ecological balance and decline of fishery resources, etc. The author of this paper suggested that we should make comparison and selection to different schemes about sluice location, methods of engineering distribution and dispatching operation from the angle of reducing the adverse effects of building sluice on the river estuary, achieving the greatest degree of unification in social benefits, economic benefits and environmental loss of building sluice on the river estuary.