The object of the present paper is to find how the generator saturated parameters changing under various steady-state conditions. In order to find the physical causes of saturation, magnetic field distributions of a 300 MW generator in various operating states are obtained based on finite element method. Through magnetic field analysis we find that two main factors influence on the generator saturation, the iron saturation and the magnetic field distortion. The exciting leakage field, terminal voltage and power angle are the terminal quantities affecting generator parameters. An estimation scheme is then designed based on above study. First, large disturbance data are simulated by a time-stepping finite element model of a synchronous generator connected to infinite bus via a transformer with delta-star connection. The linear parameters are estimated using above data. Subsequently, the steady state of operating data under various conditions are calculated by FEM. Based on the linear parameters estimated above and steady-state operating data, saturated parameters X_ad and X_aq are calculated with certain condition changing and other terminal quantities of generator keep constant to separately research on the influence of these factors on the parameters. (6 pages)