Abstract: In view of the low interpretation accuracies of watered-out zones especially fresh water flooded zones and mixed watered-out zones with conventional logging data, this paper presents an interpretation model to calculate reservoir water saturation with dielectric logging data. Application in the Xiaermen oilfield shows that the interpretation accuracies of the fresh water flooded zones and the mixed watered-out. zones with the dielectric logging data are high and the interpretation coincidence rate is up to 80%. Attentions should be paid to the influences of reservoir lithology and dielectric frequency dispersion effect and further research is needed to establish a specific modification formula.