The microstructure of Ni-based self-fluxing alloy thermal sprayed coating was investigated by microanal ysis methods.The sprayed coating was produced by the oxygen-acetylene gas flame spraying Ni-16.9Cr-3.5B4.5Si-4.6Fe-0.83C system alloy powder onto a common steel substrate.Different phases can be recognized from the morphology in the metallographic images and SEM images of compounds of high magnification.The TEM images of the (Cr,Fe,Ni) superlattice phase particles can be obtained in dark field,and the particle size is between 20 nm and 60 nm.The electron diffraction patterns of the superlattice phase and Ni-based solid solution phase can be found,as analyzed by the EDAX spectra chemical composition analysis method.