The relation between the incident angle of a p-polarization beam and the reflectance ratio on both sides of glass or other transparent material, is strongly sensitive to the surface layer parameters such as refrative index, thickness, and absorption, especially when tho refractive indexes of the surface and the flat host are nearly the same. The paper gives the primary experimental results and the numerical simulation based on the theory of thin film optics. By means of data fitting, we are able to learn the physical state of the surface layer from the experimental curves of reflectance ratio versus incident angle. The meuhode has the advantage of simplicity in equipment and easiness1 in understanding.