The historical background and extensive application of the optical tunneling effect are reviewed. Meanwhile，theoretical evidences of the evanescent field and its properties field are analyzed. Through the review and the analysis，the corresponding evanescent wave transmittance formula is obtained. Theoretically，the relationship between transmittance and the thickness of the gap，the relationship between the wavelength of the incident light and the angle of incidence are imitated. Experimentally，the relationship between the transmittance and the thickness of the gap is proved to exist.