Abstract: The Yinggehai Basin, South China Sea, offers advantages for implementing offshore CCUS (Carbon Capture, Utilization and Storage), but the basin-scale suitability and storage potential remain insufficiently quantified. To assess the geological suitability, estimate storage capacity, and propose a provincial CCS planning framework for Hainan, based on integrated geological, borehole, and seismic datasets, we analyzed stratigraphic pressure-temperature conditions, reservoir-caprock assemblages, and depositional facies in the Yinggehai Basin to delineate suitable areas and favorable structural targets for CO₂ storage. The storage potential estimates were combined with Hainan provincial CO₂ emission characteristics to inform offshore CCS planning recommendations. The Yingdong Slope and the Lingao Uplift meet the temperature-pressure and reservoir-caprock requirements for CO₂ geological storage and thus were identified as the basin’s secondary structural units most suitable for saline aquifer storage. The estimated effective storage capacities are 2.13 Gt and 1.06 Gt, respectively. Two favorable structural targets were located: HK30-3 and LG20-1, where the estimated effective storage capacities are 43 Mt and 343 Mt, respectively. Notably, HK30-3 lies at an approximate straight-line distance of only approximately 100 km from Hainan’s major industrial centers and is therefore suitable as a demonstration target for ten-million-ton scale offshore CCS in Hainan. The Yinggehai Basin possesses the geological conditions required for offshore CO₂ geological storage and exhibits billion-ton scale effective storage capacity. This study provided a scientific basis for Hainan Province to realize carbon neutrality toward net-zero emissions in coastal regions.