Due to the practical parameter determination of oil saturation model influences the utilized effects of the established model, so the determining method is very important for the modeling process. Because of the influences of the borehole surroundings, well logging resolution and so forth, there are a certain differences between the resis- tivity logging value and core resistivity, thus the measured value of the latter cannot directly applied to optimize the parameters. Therefore with the help of the calculating method of the core resistivity by well loggings, the resistivity model parameters can be determined for the effective media. The average relative error of the water saturation calcu- lated by the model is 5.2% and meets the error requirements (8%) of reservoir regulations.