<p>Marine propellers with a hollow structure may experience a lock-in phenomenon under vortex-induced vibration (VIV), potentially triggering structural damage. Based on a simplified model of hollow propeller, a shell structure hydrofoil model was established in this paper. The two-way fluid-structure interaction (FSI) method was employed to simulate the interaction between trailing vortex shedding and the hydrofoil structure by integrating the finite volume solid stress method and the shear stress transport (SST) <i>k-ω</i> turbulence model. The effects of the arrangement and number of fixed-points, as well as the shell structure, on the hydrofoil lock-in phenomenon were studied. The results show that relocating the fixed-points rearward does not affect trailing edge vortex shedding under non-lock-in conditions, but elevates the structural natural frequency of the hydrofoil and shifts the lock-in region toward higher flow velocity ranges. Increasing the number of fixed-points results in a distinct upshift in the natural frequency, shifting the lock-in region substantially upward. In the lock-in regime, a “weak lock-in” phenomenon may be observed, characterized by a vortex-shedding frequency that lies to the right of the natural frequency. In addition, for shell-structure hydrofoils that have a 2 mm skin thickness and a fixed-point at the 0.3 chord length position, the natural frequency is comparatively reduced, resulting in the susceptibility of such hydrofoils to lock-in at low flow velocities. In the frequency-domain curve of the lift coefficient for the shell-structure hydrofoils, in addition to the primary peak associated with the vortex-shedding frequency and the secondary peak linked to the structural natural frequency, a distinct third peak can also be identified. A linear relationship between this third peak and the incoming flow velocity is clearly demonstrated.</p>