Abstract: Lingdingyang estuary is a weak tidal estuary with an average tidal range of 0.86~1.69 m and the maximum of 2.29~3.36 m.Tidal impact is stronger than runoff in this estuary,so tidal movement is the main dynamic factor for river topography foundation.A physical model of flow field in Lingdingyang estuary is used to study hydrodynamic impacts after the construction of the Hong Kong-Zhuhai-Macao Bridge.The research results show that the impacts caused by the construction of HZMB are very strong appearing around the man-made island in the east and a little bit weak on the west areas of the bridge;the area near the bridge has a significant change of tidal level and flow field;and the area 5,000 m away from the bridge has a tiny change.