<p>In this paper, a numerical study is performed to investigate the hydrodynamic responses of a floating platform equipped with a heave plate adjacent to a partially reflective vertical wall. Based on the linear potential flow theory, a three-dimensional (3D) boundary element method (BEM) model, incorporating an image Green’s function, is developed to solve the wave radiation/diffraction problem in the presence of a partially reflective wall. The results confirm the efficacy of the heave plate, and the hydrodynamic response is governed by the reflection coefficient of the coast and the dimensionless distance between the coast and the platform (<i>C/W</i>_<i>b</i>, where <i>C</i> and <i>W</i>_<i>b</i> are the offshore distance and the width of the floating platform). Compared with open water conditions, the increasing of reflection coeffect suppresses surge motion but amplifies heave motion in the lower frequency region (<i>ω</i> &lt; 0.5 rad/s). Moreover, the surge motion in the lower frequency range increases and the peak heave motion decreases as <i>C/W</i>_<i>b</i> increases within the range of 0.5–3 rad/s.</p>