Abstract: Some analytical methods including XRD,SEM and TEM were used to study the surface microstructure of oriented silicon steel,and the effect of insulating coatings on the iron loss of oriented silicon steel was analyzed with a magnetic property gauge.The results show that the insulating coating consists of two layers,one is Mg₂SiO₄ and the other is a phosphate coating.No diffusion occurs between the substrate and the Mg₂SiO₄ layer,indicating that adhesion is dependent on the shape of Mg₂SiO₄ crystal grains.Some Mg₂SiO₄ grains grow into the substrate and enhance the coatings' adhesion,but increase the iron loss.