The using of nanotechnology in the welding process has great importance in developing the mechanical properties of welding joints for metals. This paper investigated the effect of addition TiO 2 NPs to welding joints to improving the Impact toughness property of the welding joints. The cold spray coating method of the nanoparticles are used to adding the TiO 2 NPs to the welding joints during the welding process. Three weight fraction are used for TiO 2 NPs (0.75%, 1.5%, and 2%). The testing samples were prepared for Impact test, and microstructure by SEM. The results show the increasing in Impact toughness of welded joints with an increase of TiO 2 NPs concentrations. The average Impact toughness for the welded sample without TiO 2 NPs. was (162.4 J), while the average Impact toughness for the welded sample with (1.5)% TiO 2 NPs. was (231.2 J) with improving rate of (42.36%). The Microstructure images by SEM show the adding of TiO 2 NPs decreases the grain size and homogenous region in welded joints cross-section compared with a sample without adding TiO 2 NPs. The EDS analysis show that increase Ti contain and decrease (Mn and Si) contain with increase TiO 2 NPs.