The reflection spectra of the one-dimensional (1D) photonic crystal is researched with the transfer matrix method. The variation characteristics of bandgap of TE and TM modes with rectangular size were analyzed in detail. The results indicate that single mode propagation of the highest mode can be obtained in 1D rectangular restricted photonic crystal, and the smaller the size of rectangular is, the easier single-mode propagationis. The structure with X=1 and Y=1 is the best one.