This paper introduces a design scheme that is capable of significantly reducing the empty ship weight, and evaluates the impact of hull weight reduction on EEDI index. Based on the design conditions of the high-speed vent valve pressure of 150,000-ton shuttle tanker, the structural weight of cargo oil tank can be effectively decreased by modifying the strength level of hull plate and structural dimension parameters in this study. Also, the safety of the weight-reducing structure is confirmed by FEA. And, the effect of hull weight reduction on EEDI is analyzed. The results show that the hull structure of the 150,000-ton shuttle tanker is reduced by about 1464 tons compared with the mother ship, and EEDI index can be reduced from 3.06 g-CO2/ton.mile to 3.03 g-CO2/ton.mile by 1.0% if the weight reduction space is used to increase the cargo load capacity. The structural weight reduction scheme and reliability evaluation method of shuttle tanker in this paper can provide reference for the design of the same type ships.