Abstract: The motion responses of complex-shaped floating bodies under wave action involve several challenging issues, including free-surface evolution, large-amplitude body motions, and the treatment of irregular wall boundaries. When the single-resolution Moving Particle Semi-implicit (MPS) method is employed, high-resolution particles generally need to be distributed throughout the entire computational domain to ensure numerical accuracy, resulting in substantial computational cost. To address this issue, a multi-resolution MPS-rigid body coupling algorithm based on the Ghost Cell Boundary (GCB) model is developed to simulate the motion responses of complex-shaped rigid floating bodies subjected to regular waves. In the proposed method, fluid motion is described using the Lagrangian MPS formulation, while the floating body is treated as a rigid body without elastic deformation. To overcome the difficulty in imposing wall boundary conditions on complex-shaped body surfaces, the GCB model is introduced to enable convenient and accurate treatment of complex boundaries. Meanwhile, high-resolution particles are employed in the wave-body interaction region, whereas low-resolution particles are used in the far-field region, thereby achieving a balance between computational accuracy and efficiency. The effective interaction range between particles of different resolutions is determined according to the particle spacing. A larger particle spacing corresponds to a larger effective interaction radius, whereas a smaller particle spacing leads to a smaller interaction radius. The motion state of each fluid particle is determined collectively by its neighboring particles within the support domain of the kernel function. A numerical program was independently developed in Fortran to implement the proposed algorithm and associated computational capabilities. First, a numerical wave-generation function was incorporated into the program and validated through representative benchmark cases. Subsequently, numerical simulations of regular-wave interactions with both freely floating and moored bodies were conducted. Comparisons with results reported in the literature and those obtained using commercial software demonstrate the validity of the developed coupling algorithm. Finally, the motion responses of complex-shaped floating bodies subjected to regular waves were investigated, further confirming the applicability of the proposed numerical method to marine engineering problems.