Abstract: The application of green ship technologies, such as hull form optimization, has been widely studied for improving energy efficiency during ship operation. However, environmental evaluations of the shipbuilding and scrapping stages remain insufficient, making it difficult to assess the lifecycle environmental impacts of these technologies holistically. To address this gap, this study selects a 150,000-ton shuttle tanker as the research object. Experimental measurements and statistical analyses were conducted to quantify differences in energy and material consumption over the ship's lifecycle resulting from hull form optimization. Using the Life Cycle Assessment (LCA) method implemented in SimaPro V9.6 software, an environmental impact assessment was performed to analyze the effects of hull form optimization on Global Warming Potential (GWP) and its contribution to carbon emission reduction. The results indicate firstly that the carbon reduction contribution of hull form optimization is highest in the shipbuilding stage, followed by the operation stage, and lowest in the scrapping stage. This suggests that a comprehensive evaluation of green ship technologies should account for not only the operational phase but also the construction and dismantling phases. Furthermore, while both LCA and the Energy Efficiency Design Index (EEDI) methods show broadly consistent trends in assessing the carbon reduction effect of hull form optimization during operation, the LCA results are more conservative. This discrepancy arises partly from differences in operational condition assumptions and the fact that the carbon emission factors in the Ecoinvent-3 database, commonly used in LCA, do not fully account for fuel combustion processes.