Fe-based amorphous powder cored wire with a wide composition window, excellent corrosion resistance, and thermal stability was obtained by adjusting the mass ratio (M) of 430 stainless steel to alloy powder. The thermal stability of the Fe-based amorphous powder cored wire was studied by differential scanning calorimeter (DSC), and its corrosion resistance in 3.5% NaCl solution was characterized by electrochemical impedance spectroscopy (EIS) techniques. The semi-conductor characteristics and compactness of the passivation film of Fe-based amorphous powder cored wire were analyzed by Mott–Schottky theory. The results show that the thermal stability of the Fe-based amorphous powder cored wire first decreases then increases with the increasing of M value. In 3.5% NaCl solution, the corrosion resistance of the Fe-based amorphous powder cored wire first increases then decreases with the increasing of M value, but is totally stronger than that of 430 stainless steel. The passivation film of the Fe-based amorphous powder cored wire has the characteristics of n-type semi-conductor in the range of 0.3–0.85 V, and its compactness increases first and then decreases with the increasing of M value.