Abstract: By choosing Ti-based alkaline slag and Mn-Ni-Si-Ti-B alloy system, a kind of seamless flux cored wire named TME711NiSF with super low hydrogen and high toughness was developed on the seamless flux cored wire production line imported from Germany. The seamless flux cored wire has excellent welding technology, mechanical properties and better adaptability to heat input. In order to investigate the toughening mechanism of deposited metal, the contents of deoxidizer and alloying agents in the formulation were optimized. The results show that when the contents of Mn, Si were at the optimized levels, the microstructure was mainly composed of uniform and fine acicular ferrite with good ductility and toughness. The -40 ℃ impact absorbed energy of deposited metal can reach up to 154 J. The diffusible hydrogen content in deposited metal reached the super low hydrogen level with 2.4ml/100 g. It can be applied in welding important steel structures of ships, bridges and marine engineering, etc.