The work aims to study hot corrosion behavior of Ni-base alloy coatings with various Ni and Cr content in simulated fuel gas prepared by HOVF, and compare corrosion resistance of the coatings. Corrosion mechanism of Ni-base alloy coating was discussed in brief. Ni-base alloy coatings with various Ni and Cr content were prepared on 20# steel substrate by high velocity oxyfuel spraying (HOVF). Hot corrosion tests were performed to the samples coated with 75%Na2SO4+25%NaCl mixed salt film in 0.15% SO2 simulated flue gas at 750 ℃ to obtain corrosion dynamic law was obtained. Composition, structure, morphology of the coatings and high temperature corrosion products were investigated by using XRD, SEM and EDS. The Ni-base coatings prepared by HVOF were dense with porosity of 0.84%. A little oxides were detected in the coating as well. All samples were first subject to mass gain and then mass loss during corrosion. The corrosion products were NiO, NiCr2O4, FeCr2O4 and (Fe,Cr)2O3. The corrosion products had bilayer microstructure, Ni-enriched external layer and Cr-enriched internal layer. The coating with 64wt.% Ni and 23wt.% Cr exhibits good corrosion resistance in the test environment.