To optimize the design of the mooring system for semi-submersible photovoltaic platforms, a numerical calculation model is established using Ansys-AQWA software combined with measured wave load conditions in the Bohai Bay. After verifying the model accuracy through scaled model tests, the response laws of mooring forces are analyzed under different wave height and period conditions for regular waves (Stokes waves) and irregular waves (JONSWAP spectrum) in nearshore shallow waters. The results show that under working conditions with wave heights ranging from 0.5 m to 2.0 m, the mooring force on the wave-facing side is significantly positively correlated with wave height, and its amplitude and extreme peak value are greatly increased with the increase of wave height, reaching 3.224 t under regular waves with a wave height of 2.0 m and a period of 7 s and 30.187 t under irregular waves with a wave height of 2.0 m and a period of 5 s, while the mooring force on the leeward side is barely affected by wave height and mainly functions in positioning. The influence of wave period on mooring force is related to wave height, with short-period waves exerting a more significant effect under small wave heights and the platform being prone to resonance near its natural pitch period under large wave heights, thus intensifying the fluctuation of mooring forces. The research results provide a key reference for the structural optimization and extreme load prevention and control of the mooring system for semi-submersible photovoltaic platforms.