The over-voltage inrush into generator stator windings can be calculated using the stator winding equivalent circuit model. But the traditional stator model cannot accurately represent the stator's electromotive force in realistic working conditions. An active stator winding model is presented by considering the electromotive force resulted from the relative movement of the stator winding with respect to the magnetic fields. Every stator slot will produce electromotive force with different phase angles， while putting the electromotive force into every sub-bar of the winding model and subdividing it. The novel stator winding model reflects the true electrical characteristics of the stator winding. The over-voltage simulation result shows that the novel model has high accuracy in calculating stator transient process.