In view of the low-resistivity reservoir caused by the high irreducible water content, this paper presents a model for oil-water relative permeability based on percolation theory of multiphase fluids in porous media and lab. experimental results, using multiple non-linear regression method, by which such a reservoir can be evaluated using oil-water relative permeability data, on the basis of exact determination of water saturation and irreducible water saturation. The study indicates that this method is simple to use and makes the success ratio of interpretation greatly improved.