Impact toughness is an important criterion in the quality of welded joints. Therefore, optimizing technological parameters to improve the impact toughness of the joint is very necessary. In this study, by experimenting and optimizing welding technological parameters in submerged arc welding (SAW) to improve the impact toughness for narrow gap butt weld joints with SS400 steel. Conducting Taguchi experimental design with L9 orthogonal array combined with ANOVA analysis of variance to optimize technological parameters including: current intensity (Ih), welding speed (Vh) and welding voltage (Uh) to the impact toughness of weld metal. The results found the optimal set of technological parameters to improve the impact toughness in welded joints and their effects. The reliability of the research results was re-examined by experimental verification.