Optical reflectance spectra of an annular dielectric mirror have been theoretically calculated and investigated based on the transfer matrix method for the cylindrical wave. The numerical results reveal some fundamental features about the annular mirror. It is found that the reflection response at azimuthal mode m = 0 for an annular mirror is almost identical to that of a planar mirror with the same material parameters. The dependence of reflectance spectrum on the starting radius in an annular mirror is shown to be very weak. In addition, for a higher azimuthal mode such as m = 1, the difference between the E-polarization and H-polarization can be seen. The upper wavelength bandedge will be lowered down in the H-polarization.