A non-inrush voltage regulating method is proposed for on load tap changer transformer by using the power electronic devices. In this method， the changes of leakage resistance and inductance caused by the change of regulating wires are taken into account. In order to consider the ferromagnetic characteristic， the iron core of transformer is modeled as a nonlinear resistance and a nonlinear inductance. According to the data of no-load experiments， the piecewise linear expressions used to describe the nonlinear characteristic are acquired. By the analysis of the equivalent model of transformer， the expressions to determine the non-inrush moment of regulating process are derived. If the on-off control of tap changer is conducted at this moment， the macrocosmic voltage is changed in terms of the demand of system operation; while the waveform of the microcosmic current is smooth， continuous and non-inrush. The conventional method that the regulating moment is determined by the impedance angle of load is a special example of the method presented here. The results of simulation and experiments demonstrate the proposed method can achieve fast， non-inrush and reliable voltage regulating process.