Abstract: A two-dimension nonlinear wave-load numerical model in a time-domain is developed for the fluid resonance induced by the interaction between wave and fixed rectangular multi-boxes with narrow gaps. In the proposed model, the incident wave is generated by the inner-domain sources. The fully nonlinear kinematic and dynamic boundary conditions are satisfied on the instantaneous free surface. An artificial damping is introduced into the free surface of gaps to approximate the viscous dissipation due to vortex motion or flow separation. The corresponding boundary integral equation is founded and a higher-order boundary element method is used to discretize and solve it. Then the acceleration potential technique is adopted to calculate the temporal derivative of the potential on the body surface, and transient wave loads are obtained by integrating the Bernoulli equation along the wetted object surface. By the comparison with the published numerical results of the horizontal and vertical forces in the case of two narrow gaps of three boxes, the proposed model is validated. Numerical experiments are further performed to study the effects of the number of the boxes on the wave loads on the boxes and their variation rules.