Lingdingyang Firth of the Pearl River Estuary is a sensitive sea area with unique geomorphic features and complex hydrodynamic sediment conditions,and it is also one of the coastal sea waters with densest routes and biggest ship density.The Hong Kong-Zhuhai-Macao Bridge (HZMB),consisting of bridge-islands-tunnel,is a super large complex project crossing the Lingdingyang Firth.Aiming at HZMB and complex hydrodynamic sediment environments of Lingdingyang Firth,various means are adopted to carry out comprehensive and deeply studies on the key problems such as the influences of HZMB on hydrodynamic sediment environment,harbor and navigational channel and stability of shoals and troughs,etc.The following main conclusions are drawn from the study.1)Lingdingyang Firth of the Pearl River Estuary presents the characters of micro-variability,tendency-to-stability and flexibility,and its geomorphic pattern of “Three Shoals and Two Troughs” can keep stable chronically.2)The recommended scheme of HZMB has relatively less influence on hydrodynamic sediment environment,and it has bascially little unfavorable impact on harbors and navigational channels.3)The recommended scheme of HZMB is feasible as far as its effect on hydrodynamic sediment environment is concerned.