The time-harmonic electromagnetic wave through the one-dimensional photonic crystals (1-D PCs) perpendicularly has been considered. By theoretical calculation with characteristic matrix method, the dispersion curves and the transmittance spectra were calculated. From the dispersion curves, it shown that the lowest band gap is at frequencies between 0.23~0.32, i.e. it is around 0.27. In addition, according to the transmittance spectra, it shown that the transmittance declined from 40.6% to 0 dramatically along with the periodicity N of the periodically stratified medium increased from 2 to 1024, it also exhibited that when the periodicity N was upped to 8, it could form 1-D PCs.