Abstract: Here was studied the influence of Ni contents in the flux cored wires on microstructure and mechanical properties of deposited metals, and the microstructures were analyzed with the help of thermodynamics software Thermal-Calc. The result shows that Ni has a significantly strengthening effect and that with the increase of Ni content, the tensile strength increases while the impact toughness goes down gradually. With the increase of Ni content, the transformation temperature of austenite decreases gradually and the volume fraction of primary ferrite decreases and the amount and size of the precipitated coarsening carbides increase. When Ni content increases to some degree, M-A constituents appear.