The isothermal oxidation behavior of Hastelloy N superalloy with different silicon contents in air at 850℃ were investigated by using discontinuous increasing weight method. The results showed that oxidation mass gain kinetics of the samples follow the parabolic law. It was observed that the surfaces of the alloys exhibited a multi-layer structure after 100h oxidation. The outer oxide flim of Hastelloy N superalloy mainly consists of NiO, NiFe₂O₄and other oxide composites. The middle layer is confirmed to be Cr₂O₃ and MoO₂. Since a continuous and dense SiO₂ sublayer is formed at the metal-oxide interface, it is effective to prevent Cr diffusion. The addition of Si promotes the formation of a relatively continuous and compact Cr₂O₃ and it can strongly improve the oxidation resistance.