Offshore photovoltaic power generation represents a novel approach to energy utilization. By conducting horizontal static load tests on steel pipe pile foundations in layered offshore soils, we obtained the variation patterns of pile bending moments and displacements with depth. A modified hyperbolic model for p-y curves (showing the relationship between horizontal soil resistance and pile displacement) was proposed, which was compared with existing specifications and conventional hyperbolic models. The results indicate that the piles undergo rigid deformation, with maximum bending moments occurring at 7D (where D denotes pile diameter) below the mudline. The API (American Petroleum Institute) specification was found to overestimate initial stiffness while underestimating ultimate resistance, whereas the conventional hyperbolic model underestimated both initial stiffness and ultimate resistance. The proposed modified hyperbolic model, incorporating pile diameter and stratigraphic variations, demonstrated a 55–70% reduction in prediction errors. This advancement provides enhanced applicability for the design of offshore photovoltaic piles in layered soil conditions.