In the paper the efficient and low-cost plasma cladding technique has been used to prepare Fe-Ni based alloy coatings on the surface of low carbon steel. The high-temperature isothermal oxidation behavior of the specimens has been tested at 700 °C and 800 °C in air using an electrical furnace for 100 h. The elements distribution, phase composition, and morphology of the alloy coatings after the oxidation test have been characterized by SEM/EDS and XRD. Isothermal oxidation test show that the Fe-Ni based alloy coating has excellent high temperature oxidation resistance at 700 °C and 800 °C. The oxidation rate of Fe-Ni based coating at 800 °C is higher than that of at 700 °C. At 800 °C, the oxidation kinetics basically follows the parabolic rate law before 80 h. A protective Fe0.99Fe1.97Cr0.03Ni0.01O4 and Cr1.3Fe0.7O3 based oxide film has been formed on the surface of the coating after oxidation.