A calculation model of electromagnetic field of transmitted-aperture(TA) type super-resolution near-field structure(super-RENS) disk based on three-dimensional finite-difference time-domain(3D-FDTD) method and a vector method of Gaussian beam was presented.Lorenz dispersive model was employed for mask layer material Sb and reflective layer material A1.The distributions of electric field for TA type super-RENS during writing and reading process were theoretically analyzed,as well as that of traditional CD-R/W.The calculation results described the electric field properties of TA type super-RENS and discovered the fundamentals of super-resolution essentially.The theoretical results were satisfied with the experiments very well.