Polar ships sail in low-temperature Polar Regions all year round and are often collided with floating ices. The welding joints of polar ships therefore demand high comprehensive performance. The microstructure and mechanical properties, residual stress and deformation of the electrogas welding (EGW) are systematically analyzed for the polar ship equipment. The optimization of the welding process of the EGW, improvement of the reliability of the welding joints and reduction of the welding deformation and residual stress promote the application of efficient welding processes for polar ships. The results show that with the increase of groove gap, the linear energy increases, the low-temperature toughness stability of the weld decreases, and the low-temperature toughness of the heat-affected zone decreases significantly, as well as the residual stress and deformation of the weld increase significantly. The large heat input steel plate developed by the technologies of oxide metallurgy or oxidation metallurgy can effectively improve the low-temperature toughness of the heat-affected zone and the reliability of the welding joints.