Magnetic properties of conventional grain-oriented electrical steel sheets are different in various directions, Epstein standard samples were cut with different angles to rolling direction and the corresponding magnetic properties of samples were tested. Experimental results shows that the hard magnetization direction is around 60°to the rolling direction. Conventional elliptical models are not accurate to simulate permeability at all magnetic intensities, and parabolic and hybrid models with high accuracy were proposed to simulate relations between permeability and magnetization direction. When magnetic intensity is no less than 10000 A/m, hybrid model could be used, and when magnetic intensity is less than 10000 A/m, parabolic model should be applied. Two-stage relation model of permeability and magnetization angles is significant in improving the accuracy of electromagnetic engineering calculations of electrical steel and could be applied in industrial applications.