Abstract: Taking T492T1-1C1A flux cored wire as an example, the influences of different additions of MnO in the formula on the weld structure and the mechanical properties of the deposited metal is studied by comparing and analyzing the slag composition, metallographic structure and chemical composition of the deposited metal, diffusion hydrogen content and mechanical properties. The results show that with the increase of MnO addition, the contents of Mn and O in the deposited metal do not show significant changes. The elongation and low-temperature impact absorption work of the deposited metal increase first and then decrease. Better weld microstructure and mechanical properties are obtained when the mass fraction of MnO is 0.5%. The diffusion hydrogen content of the deposited metal tends to decrease.