In combination with the design of waterfront excavation for a ship dock entrance, a twodimensional finite element numerical simulation is conducted to investigate the performance of the retaining structures during the excavating and dewatering process of the dock entrance. The geotechnical analysis program Plaxis 2D is adopted to establish the plain-strain numerical model which takes into account the interaction between the retaining structures and the surrounding strata, different tide levels and wave conditions, on-site topographical and geological conditions, as well as the complicated construction sequences. The numerical results indicate that there are obvious distinctions of the performance of retaining structures between waterfront excavation and conventional onshore excavation. The most disadvantageous construction stage of the waterfront excavation is during the process of dewatering and before the construction of protecting berms outside the retaining steel sheet piles. Tide and wave conditions exert more detrimental impacts on the single-line steel sheet piles than on the doubleline compound steel sheet piles filled with sand. More concerns should be focused on the alteration of the axial force of the first-level struts which may change from compression to subsequent tension; correspondingly, the overall cast-in-situ concrete beams ought to be used for the first-level struts to strengthen the integrative stiffness of the retaining structures.