In order to improve the oxidation resistance of IN 718 coating, 2wt.%Si powder was added into IN 718 Ni-based powder to prepare coating on H13 steel surface by plasma cladding technique. The coating was separated from the substrate by wire cutting. The cyclical oxidation experiments at 900 ℃, 1000 ℃ and 1100 ℃ respectively were carried out in a high temperature furnace in static air. The high temperature oxidation resistance of the Si-modified IN 718 coating was tested. The changes of microstructure and composition of the coating and its oxide layer were analyzed by XRD, SEM and EDS. The addition of Si changed the microstructure of the coating, increased the content of equiaxed crystal, and improved the microhardness of the coating. The oxidation kinetic curves of the two coatings at 900 ℃ were basically the same, and the oxide layers were all Cr2O3. IN 718 oxide layer was Cr2O3 at 1000~1100 ℃. According to the Thermo-calculation result, the Si activity was greatly increased above 900 ℃, which results in that a double layer of oxide layer was genarated on the IN 718+Si coating at 1000 ℃ and 1100 ℃, the outer layer was Cr2O3, and the inner layer was SiO2. The high temperature oxidation resistance of IN 718 coating over 1000 ℃ was improved owing to Si addition.