The welding process, which accounts for about 60% of the shipbuilding process, inevitably involves weld deformation. Considering this, productivity can be significantly increased if weld deformation can be predicted during the design phase, taking into account the fabrication order. However, the conventional welding deformation prediction method using thermo-elasto-plastic analysis requires a long analysis time, and the welding deformation prediction method using equivalent load analysis has a disadvantage in that the welding residual stress cannot be considered. In this study, an inherent strain chart using a solid-spring model with two-dimensional constraints is proposed to predict the equivalent strain. In addition, the welding deformation prediction method proposed in this study, the equivalent strain method (ESM), was compared with the ship block experimental results (EXP), elasto-plastic analysis (EPA) results, and equivalent load analysis (ELM) results. Through this comparison, it was found that the application of the equivalent strain method made it possible to quickly and accurately predict weld deformation in consideration of the residual stress of the curved double-bottom block used in the shipyard.