Abstract: With the acceleration of the world’ s energy transition process and the establishment of the China’ s dual carbon targets, offshore floating photovoltaics（PV） have become an important form of marine new energy.According to the current problems of Offshore floating PV development being constrained by unclear cost benefits and unknown development prospects.Firstly, the cost of inland floating PV and sea-related technology to determines the offshore floating PV sub-items cost.Secondly, through calculating the economic index of photovoltaic system cost, it analyzes the offshore floating PV economy from many angles.Finally, it predicts the future cost of offshore floating PV by historical economic data.The results show that the cost reduction of offshore PV projects over the next decade is significant.In 2024,the project will realize revenue and expenditure balance due to the subsidy policy.After 2026 subsidy withdrawal, the project can be profitable independently.