Abstract: The water saturation distribution model is an important part of water displacing oil theory. It is often used in theoretical analysis of water-driving-curve and processing of experimental parameters of core displacement. Aiming at problems such as difficulties in field application because of the non-linear characteristics of the expression between water saturation outlet and average water saturation in the oil-water two-phase zone, and significant deviations in the later stage of the development of the Bolysov model, a new simple and practical model for water saturation distribution was established based on the theory of non piston water flooding and the definition of water content. By X-CT scanning the results of water flooding experiments, the axial water saturation distribution of the core was quantitatively characterized, combined with the monitoring data of residual oil saturation in production wells of the field, through normalization data processing, the rationality of the double logarithmic relationship between the average water saturation and the outlet water saturation was testified. The accuracy is improved in application during medium to high water cut periods. The establishment of a new water saturation distribution model provides strong technical support for evaluating the development potential of water drive reservoirs in the field scale and studying the distribution pattern of remaining oil. It is of great significance for increasing production and tapping potential in water drive oil fields.