The experiments of crack propagation at the corner of the porthole structure are reproduced to study the impact of the cracks on the porthole structure of cruise ships by using the finite element software, which verified the feasibility of the current research method. Two types of porthole structure models are then established to discuss the crack propagation characteristics at the corner of the porthole structure under different factors by using the crack propagation software. The ultimate compressive strength of the porthole structure with cracks is also calculated. Finally, the ultimate state function of the porthole structure is proposed based on the improved Paris formula from the viewpoint of fracture mechanics. The failure probability and reliability index of the structure under different conditions are calculated by the Monte Carlo method. The results can provide references for the design of luxury cruise ships.