Abstract: The accuracy of diode model in the demagnetization protecting circuits has the impact on the results of the circuits calculation design and analysis. This paper presents the calculation of current response and power dissipation of the demagnetization protecting circuits by using the equivalent voltage source model and the equivalent resistor model of diode group firstly. Then a new nonlinear model is proposed based on curve fitting method of current-voltage characteristic of the real diode to overcome the disadvantages of two diode models and improve the accuracy of calculation. Finally, the simulation results proved that the equivalent voltage source model and the nonlinear model have better effects on calculation and analysis.